Binaural bass crackling: How to fix/avoid?

Greg Miller · January 25th, 2011, 11:43 AM

Thanks, Steve.

Micky said he did use Audacity the last time around. Since the resulting file was 96kHz, and the R-09 only goes up to 48kHz, Audacity apparently changed the sample rate without Micky's conscious consent to do so.

So my fear is that it may have made some other unknown changes, too... level, normalization, who knows what all? (And once the software has changed the samples, it will be harder for us to see what was actually recorded.)

I'm looking for something essentially foolproof, so that he can send a short snip, without our worrying that the software has made changes in the actual sample values.

Meanwhile, as a fallback, Micky can upload the entire 1GB file... but IMHO a nice *unaltered* snippet would be a lot easier to deal with.

Micky Hulse · January 25th, 2011, 12:08 PM

Hi Greg and Steve! I can't thank ya'll enough for the help! I am learning a ton, and I totally appreciate all of the professional help here!

@Steve:

Your theory would definitely explain a lot of things. I wish I could re-visit the Planetarium to find out! I probably did not notice the "pops" because I had the mics in my ears (and I was having some inner-ear popping myself when I swallowed.)

Are any of you near S.F.? The audio recording was made during the "Life: A Cosmic Story" exhibition at Morrison Planetarium, California Academy of Sciences. The story line was not the best, but the visuals were pretty amazing. It seemed like they had spent a lot of money producing the sucker... Wouldn't that be a shame if someone fudged the sound coming from the PA system! :D

This would explain why the waveform looks decent.

@Greg:

Doh! I am so sorry that I did not specify the model of the R-09! :(

I was actually using the http://www.bhphotovideo.com/c/product/559244-REG/Edirol_Roland_R_09HR_R_09HR_Portable_High_Resolution_Audio.html... A slightly newer model than the original R-09.

God, I see now that I accidentally linked to the older model in my first post! :: Slaps self on forehead ::

For all my recordings I use the 24-bit/96kHz settings.

Sorry that I did not specify earlier. I hope that I did not waste any of your time. :(

Thanks a billion for all your pro help Greg and Steve! I can't thank you enough. I definitely owe ya'll one.

Have a great day!

Cheers,
Micky

Greg Miller · January 25th, 2011, 12:58 PM

Micky,

Ouch, I wish you had been more specific, earlier, about your recorder model number. It would have avoided some confusion on my part.

However, I still think your use of Audacity did, in fact, change the file. You state that your original recording was 24bit/96kHz. However, the "snippet" you posted was only 16bit depth!

So please, before we spend any more time on questionable files, post the original, unaltered, file!!! And post a timeline of where we can find some of the clicks (a cluster of at least a dozen clicks, close together, would be really helpful).

No, I do *not* think your binaural mics recorded your ears popping! The anomalies in the file (actually I see abrupt jumps in level) occur exactly simultaneously on both channels. There is no chance in hades that both of your ears popped simultaneously, time after time after time. Forget that "ear popping" concept.

Speaker pops? I'm not quite ready to rule that out, although I the more I look at the file, the less likely I am to name that as the culprit.

Steve, by a strange coincidence, I actually worked as a tech at the "Albert Einstein Spacearium" which is the bureaucratic name of the planetarium in the National Air and Space Museum in Washington, DC, part of the Smithsonian Institution. When I was there, we did have some wretched Altec Lansing speaker cabs, which bottomed out drastically whenever the track contained any substantial amount of LF info... we had to roll off the LF effects to get a clean playback. In fact the track had been mixed at a studio with JBLs which were, of course, much cleaner. (It was embarassing... especially since the playback system in our IMAX theatre was so much better.) But that's not quite what a hear/see in Micky's files... it does not sound like speakers bottoming, and may or may not be in the playback system.

OK, Micky, waiting for a complete original file from you...

Micky Hulse · January 25th, 2011, 01:14 PM

Quote:

Originally Posted by Greg Miller

Ouch, I wish you had been more specific, earlier, about your recorder model number. It would have avoided some confusion on my part.

Ack! I know. :(

I feel pretty lame about not being more specific. Sorry about that. :(

Quote:

Originally Posted by Greg Miller

However, I still think your use of Audacity did, in fact, change the file. You state that your original recording was 24bit/96kHz. However, the "snippet" you posted was only 16bit depth!

I am not starting to feel pretty ADD... I could swear that I recorded that audio in the higher bit setting, but there could be a possibility that I was in 16bit depth mode.

Maybe before I post the full gig+ file, I will check the bit depth via Audacity? I know for sure that I have not altered the original file, and I could have accidentally chose 16bit mode instead of 24 while I was on vacation in S.F. (I might have done this to save space on the card(s)... In hindsight, I probably should have used 24bit mode because I had multiple 8gig memory cards handy).

Quote:

Originally Posted by Greg Miller

So please, before we spend any more time on questionable files, post the original, unaltered, file!!! And post a timeline of where we can find some of the clicks (a cluster of at least a dozen clicks, close together, would be really helpful).

Sounds good to me. Sorry about all the mix ups. :(

As soon as I get home from work, I will upload the source file and post a timeline.

Quote:

Originally Posted by Greg Miller

No, I do *not* think your binaural mics recorded your ears popping! The anomalies in the file (actually I see abrupt jumps in level) occur exactly simultaneously on both channels. There is no chance in hades that both of your ears popped simultaneously, time after time after time. Forget that "ear popping" concept.

Lol! Thanks for clarifying! :D

I knew that theory sounded pretty silly.

Quote:

Originally Posted by Greg Miller

Speaker pops? I'm not quite ready to rule that out, although I the more I look at the file, the less likely I am to name that as the culprit.

Interesting. Like I said, I wish I could just re-record the planetarium again... I do plan on going back down there in a few months... Maybe I will get a chance to record again! :)

Quote:

Originally Posted by Greg Miller

OK, Micky, waiting for a complete original file from you...

Thanks so much Greg! I really appreciate the help!!!! Sorry again for all the confusion. :(

I will post back asap after work.

Have a great day!

Cheers,
Micky

Paul R Johnson · January 25th, 2011, 01:35 PM

Just a thought - but did you use the battery module? The reason for asking is that if the bias voltage is supplied by the recorder, then the dynamic range of the mic is quite low - 105dB SPL (120 db when used with one of our battery modules). With so much bass, it's quite possible that the distortion are the mics itself - the recorder recording the distortion faithfully, which might also explain why the file, without being tinkered with, is at a modest level, but showing these clicks. The waveform, as mentioned hasn't flat topped, but is just spiky and rough - there's no audio peaks that cause it like snares or other percussive stuff - so could be the heavy bass components below 50Hz - which on a spectrum display seem very prominent.

Greg Miller · January 25th, 2011, 02:00 PM

Hi Paul,

Your questions are in line with my suspicions, which is why I want to see the original file.

In post #1, Micky said he had the recorder's "in line" power turned off.

In post #3, he said he was using an external battery module.

With a battery module, the mics themselves probably weren't clipping at the moderate levels one would encounter in a planetarium (lots lower than a live rock band, for example). And anyway, both mics would not clip at exactly the same time in every instance. But if he was running them into a mic input (rather than a line level input, as suggested in the instructions for that mic/module combo) then he might have overloaded the mic preamps. That would show up as some sort of anomaly in the waveform, but might have been much lower than 0dBFS depending on the configuration of the recorder.

It still strikes me as odd, though, because some of the clicks are *not* at program peaks.

For example, at about 28.707 there is a click with a level of about -5dB, but then after the click the level continues to increase to nearly -3dB without any further clipping.

Then at about 28.746 there is a click with a level of about -6dB.

So the clicks do not occur at a consistent level, and the waveform "voltage" sometimes increases after the time when the click occurs. Furthermore, the clicks occur at exactly the same *time* on both channels, even though the levels on the two channels are different. This isn't really what I'd expect if the electronics were clipping... I would expect that to happen at exactly the same *level*.

Yet the clicks occur at exactly the same time on both channels, each and every time. Could it be some sort of malfunction of the AGC circuitry in the recorder? Seems unlikely... the AGC circuitry should have some sort of reasonable attack time and should not generate audible clicks when it operates.

I really want to see the original file!

------------------

UPDATE:

A pro who really knows what he's talking about assures me that if you import a WAV file into QTPro, and trim it to the size you want, then the "export" function can save a WAV format file with the data entirely unchanged from the original file.

I don't use QTPro, so you'll have to look through your menus, settings, options, preferences, etc. and try to find the correct way to do this.

Meanwhile, why don't you tell us the exact length (hrs/mins/secs) of the original file, and the exact file size (Bytes, kBytes, MBytes, or whatever). Then we can do the math and confirm what the sample rate and bit depth were. That will help us verify whether or not your editing procedure is changing bitrate or depth.

ALSO: Are you running Windows or Mac platform?

Micky Hulse · January 26th, 2011, 12:16 PM

Quote:

Originally Posted by Paul R Johnson

Just a thought - but did you use the battery module? The reason for asking is that if the bias voltage is supplied by the recorder, then the dynamic range of the mic is quite low - 105dB SPL (120 db when used with one of our battery modules). With so much bass, it's quite possible that the distortion are the mics itself - the recorder recording the distortion faithfully, which might also explain why the file, without being tinkered with, is at a modest level, but showing these clicks. The waveform, as mentioned hasn't flat topped, but is just spiky and rough - there's no audio peaks that cause it like snares or other percussive stuff - so could be the heavy bass components below 50Hz - which on a spectrum display seem very prominent.

Interesting! I did use the battery module and the plug-in power on the R-09 was turned off.

This might be a silly question, but should I be using a battery module or is it better to use the plug-in power of the R-09HR? I assume it is better to use the battery pack (120 dB dynamic range is better than 105dB without a battery pack, no?)

I purchased the MM-CBM-Mini... This was the cheapest battery pack, but it looked like the most simple and compact. Would another style of battery pack help in this situation, or are the mics the limiting factor for when it comes to over-the-top bass?

I would be willing to buy another style battery pack if it would help me get better audio recordings.

Sorry for my lack of technical terms here, I am still learning all the lingo. :)

Quote:

Originally Posted by Greg Miller

With a battery module, the mics themselves probably weren't clipping at the moderate levels one would encounter in a planetarium (lots lower than a live rock band, for example). And anyway, both mics would not clip at exactly the same time in every instance. But if he was running them into a mic input (rather than a line level input, as suggested in the instructions for that mic/module combo) then he might have overloaded the mic preamps. That would show up as some sort of anomaly in the waveform, but might have been much lower than 0dBFS depending on the configuration of the recorder.

If I am understanding correctly, that is very interesting!

Are you saying that I might have accidentally had the R-09HR's "plug-in power" turned on? Gosh, that sure would explain a lot of things.

I am pretty positive that I kept the "plug-in power" turned off for my recordings, but I could have accidentally clicked it on. I guess that is why there is the "lock" switch. :)

Would having "plug-in power" and the battery pack on at the same time do any damage to either my mics and/or the recorder?

Quote:

Originally Posted by Greg Miller

It still strikes me as odd, though, because some of the clicks are *not* at program peaks.

For example, at about 28.707 there is a click with a level of about -5dB, but then after the click the level continues to increase to nearly -3dB without any further clipping.

Then at about 28.746 there is a click with a level of about -6dB.

So the clicks do not occur at a consistent level, and the waveform "voltage" sometimes increases after the time when the click occurs. Furthermore, the clicks occur at exactly the same *time* on both channels, even though the levels on the two channels are different. This isn't really what I'd expect if the electronics were clipping... I would expect that to happen at exactly the same *level*.

Yet the clicks occur at exactly the same time on both channels, each and every time. Could it be some sort of malfunction of the AGC circuitry in the recorder? Seems unlikely... the AGC circuitry should have some sort of reasonable attack time and should not generate audible clicks when it operates.

I really want to see the original file!

Wow, that is very curious!

Sorry that I did not get the file to you sooner:

R09_0006.WAV (1.71GB)

Here is a spot with clicks:

21:11 - 21:22

Thanks so much for all of the help Greg, you are a life saver! I am learning a ton!

Quote:

Originally Posted by Greg Miller

UPDATE:

A pro who really knows what he's talking about assures me that if you import a WAV file into QTPro, and trim it to the size you want, then the "export" function can save a WAV format file with the data entirely unchanged from the original file.

I don't use QTPro, so you'll have to look through your menus, settings, options, preferences, etc. and try to find the correct way to do this.

Meanwhile, why don't you tell us the exact length (hrs/mins/secs) of the original file, and the exact file size (Bytes, kBytes, MBytes, or whatever). Then we can do the math and confirm what the sample rate and bit depth were. That will help us verify whether or not your editing procedure is changing bitrate or depth.

ALSO: Are you running Windows or Mac platform?

I am using a Mac.

Ooh, that's good to know about Quicktime.

Here is an export to WAV from qtpro:

http://sandbox.hulse.me/R-09_BSM-8/new/R09_0006.WAV

Here is a screen shot of the QTPro settings that I was using:

http://sandbox.hulse.me/R-09_BSM-8/n...o-settings.png

Based on the Quicktime clip info:

HH:MM:SS = 00:49:24.18

Size: 1.71GB, or, 1,707,370,028 bytes

Here's a screen shot of the info window:

http://sandbox.hulse.me/R-09_BSM-8/new/qtpro.png

Thanks Greg! Thanks everyone! You folks are AMAZING! :)

Have an excellent day.

Cheers,
Micky

Greg Miller · January 26th, 2011, 03:36 PM

Hi Micky,

Thanks for sending the additional info and files.

It's a lot to tackle, as this is getting deeper and deeper. But it's interesting. I'll at least start to reply now, and will post again later with more info.

1.) An electret condenser mic is a type of transducer that converts audio energy to electrical energy. All mics have two terminals where the signal comes out. Professional mics, with a "balanced" electrical connection, have two signal terminals, plus a separate ground/shield. Consumer electret mics are "unbalanced" and one of the signal terminals is exactly the same terminal as the ground/shield. In addition, there is a "hot" terminal which does two things: it accepts DC voltage ("plug in power") coming from the recorder or from the battery box, and it supplies the audio signal back to the recorder.

Within certain limits, the signal voltage coming out of the mic is directly related to the acoustical energy going into the mic. More acoustical level produces more signal voltage. BUT there are some limits to this transfer function. For one thing, the physical reality of the mic limits the maximum physical excursion of the diaphragm. If, for example, the diaphragm can only move 0.01mm (which will be caused by some specific Sound Pressure Level) then a louder sound cannot move the diaphragm any farther than that. Another limiting factor is the DC voltage level being supplied to the mic (from the recorder or battery box). The mic output voltage cannot go any higher than the DC supply voltage (actually a bit less). So once the SPL reaches that level, the mic cannot produce any more output, even if the sound gets louder.

For most "plug in power" condenser mics, the physical limit of the mic will be higher than the electrical limit (which is related to the DC voltage). Thus, you see specs for your mic that say the maximum level it can reproduce is 105dB SPL when powered by a typical recorder (which probably provides somewhere between 1.5 volts and 3 or 4 volts DC, depending on the model recorder); or the mic can reproduce 120dB SPL when powered by the battery box which provides 9 volts DC. So when you're recording anything that might be fairly loud, you definitely should use the battery box. (The upper limit for most "plug in power" mics is around 9 volts... you probably won't find battery boxes that have a higher voltage than that.)

But now when the SPL gets loud, the voltage coming out of the mic can be pretty high... perhaps approaching 1 volt RMS. (I'm checking the specs for your specific mics.) That is too much level for most mic inputs to handle! That's why the mic's instructions say that you should always use the recorder's line input when using the battery box. And of course the line input does NOT have any "in line power" to worry about.

2.) Unless there's something really odd/bad about your present battery box, I don't think a different one would make the recordings any better.

(Actually there are some purists who say that re-wiring the mic capsules, and using a custom battery box with the positive terminal grounded, rather than the usual negative ground, will provide cleaner audio. That's way far beyond the options that are available to you. Forget I mentioned it.)

3.) I was not really suggesting that you might have had the "plug in power" turned on, at the same time as the battery box. But yet, you might have. (see #4 below) In that case, it's hard to predict what might have happened. The output voltage from the mic might have risen higher than the recorder's "plug in power" voltage. Now, both the battery box and the recorder should have resistors (at least 1k ohms, maybe as high as 10k ohms) between the DC supply and the mic connector. Those resistors should hopefully protect against damage in a situation like this. But even if there was no *damage* per se, perhaps having the recorder's "plug in power" and the battery box both connected at the same time, might cause some unexpected behavior... such as strange clicks. Perhaps we'll never know for certain.

4.) You see by now that this is in the nature of a scientific investigation. It's hard to draw conclusions without knowing all the conditions of the experiment. And you've been very openly uncertain about what you did when you made this recording. (Was the gain high or low? Was "plug in power" on or off? Etc.) Obviously since we don't know these things for certain, we may never know for certain what caused the problem. One lesson here is that you should always be sure how everything is set and connected, and hopefully make a few notes for later reference!

5.) Your file was 1,707,370,028 Bytes / 2964 seconds. That's 576,036 Bytes/second = 4,608,286 bits/second.

(96,000 samples/second) * (24 bits/sample) * (2 channels) = 4,608,000 bits/second

So yes, your original recording was 96kHz/24bits, as you originally recalled.

And that means that your previous "snip" operation did change the bit depth. So I definitely want to look at the original unchanged data, which hopefully you have sent today.

-----

I think that answers most of the hypothetical questions so far. I think this is a good stopping point for this particular post. After I have time to check the new files, I'll post again with some more info.

Micky Hulse · January 27th, 2011, 02:18 PM

Greg... One word:

WOW!

THANKS so much for all the pro information!

I am learning a ton. Awesome stuff!

I definitely owe you one. Next time you are in Eugene I will buy you a beer! :)

Thanks!!!!!

Have an excellent day!

Cheers,
Micky :)

Greg Miller · January 29th, 2011, 04:10 PM

Micky,

I have another installment for you. It includes 5 .gif files to illustrate what I'm talking about. I'm trying to find out how I can upload those files to the forum, so you can see them. As soon as I figure that out, I will post the stuff.

Micky Hulse · January 31st, 2011, 07:51 PM

Quote:

Originally Posted by Greg Miller

Micky,

I have another installment for you. It includes 5 .gif files to illustrate what I'm talking about. I'm trying to find out how I can upload those files to the forum, so you can see them. As soon as I figure that out, I will post the stuff.

Ooooh, awesome! Looking forward to seeing. :)

Last time I tried to post images unfortunately I could only link to images hosted remotely. If you want to e-mail the images to me, I can post them on my web server and link to them... Let me know.

Thanks Greg!!!!!!

Cheers,
Micky

Greg Miller · January 31st, 2011, 10:33 PM

Ah, OK. That was the only option I could find.

The forum's FAQ says that, after I click "Reply" the reply page has a "Manage Attachments" area at the bottom of the page. I don't see it; can't find it. I thought either (1.) I was missing something obvious, or (2.) I hadn't generated enough posts yet to "earn" the right to post files.

I EMailed the administrator about this question, but never got a reply.

I will see about hosting them locally and then try linking to them.

Film at eleven...

Micky Hulse · February 1st, 2011, 12:07 PM

Hey Greg!

Quote:

Originally Posted by Greg Miller

Ah, OK. That was the only option I could find.
The forum's FAQ says that, after I click "Reply" the reply page has a "Manage Attachments" area at the bottom of the page. I don't see it; can't find it. I thought either (1.) I was missing something obvious, or (2.) I hadn't generated enough posts yet to "earn" the right to post files.
I EMailed the administrator about this question, but never got a reply.
I will see about hosting them locally and then try linking to them.
Film at eleven...

Yah, I remember thinking some of the same things (missing the obvious)... I actually posted a message here:

http://www.dvinfo.net/forum/open-dv-...e-buttons.html

Back then, I was trying to post an image and have it display on these forums (vs. a link). The FAQ says "that you can wrap [img]...[/img] around an image link and have it appear as an image," but all it really does (FWIK) is make the image URL a link. :(

Quote:

Originally Posted by Chris Hurd

Links become links automatically; no button or BB code needed.
Vimeo clips become embedded in a player just by posting the URL.
If you really feel like making something bold, make the effort and do
the extra keystrokes. We're not making BB code easy or accessible
because we really prefer readable posts.

I can understand why they made these forums very vanilla for when it comes to "readable", but I think there is a good reason to have at least the basic BBCode buttons and file upload features.

Anyway, sorry if totally OT... Let me know if you need any help posting those images. :)

If you are looking for a nice way to share files between computers (and with the public via the www) I recomend Dropbox. They give you a few gigs of space for free. I love using it for sharing things like my actionscript classes, premiere presets/templates, and/or fonts across the different computers that I use.

Well, have a great day!

Cheers,
Micky

Micky Hulse · February 1st, 2011, 12:09 PM

Ahhh, you know what, I just noticed that I can upload files! I guess you do have to have XX many posts before you can use this feature. :(

Greg Miller · February 1st, 2011, 04:52 PM

Too bad I didn't see that posted anywhere in the FAQ. Maybe I need new glasses (if it's in there).

January 25th, 2011, 12:08 PM	#17
Micky Hulse Major Player Join Date: Jul 2007 Location: Eugene, Oregon, USA Posts: 213	Hi Greg and Steve! I can't thank ya'll enough for the help! I am learning a ton, and I totally appreciate all of the professional help here! @Steve: Your theory would definitely explain a lot of things. I wish I could re-visit the Planetarium to find out! I probably did not notice the "pops" because I had the mics in my ears (and I was having some inner-ear popping myself when I swallowed.) Are any of you near S.F.? The audio recording was made during the "Life: A Cosmic Story" exhibition at Morrison Planetarium, California Academy of Sciences. The story line was not the best, but the visuals were pretty amazing. It seemed like they had spent a lot of money producing the sucker... Wouldn't that be a shame if someone fudged the sound coming from the PA system! :D This would explain why the waveform looks decent. @Greg: Doh! I am so sorry that I did not specify the model of the R-09! :( I was actually using the http://www.bhphotovideo.com/c/product/559244-REG/Edirol_Roland_R_09HR_R_09HR_Portable_High_Resolution_Audio.html... A slightly newer model than the original R-09. God, I see now that I accidentally linked to the older model in my first post! :: Slaps self on forehead :: For all my recordings I use the 24-bit/96kHz settings. Sorry that I did not specify earlier. I hope that I did not waste any of your time. :( Thanks a billion for all your pro help Greg and Steve! I can't thank you enough. I definitely owe ya'll one. Have a great day! Cheers, Micky __________________ Home: See *"Work"* :) Work: Canon XH A1, CS3/CS4/CS5/Final Cut Studio/Final Cut Express/Premiere Elements

January 25th, 2011, 02:00 PM	#21
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Hi Paul, Your questions are in line with my suspicions, which is why I want to see the original file. In post #1, Micky said he had the recorder's "in line" power turned off. In post #3, he said he was using an external battery module. With a battery module, the mics themselves probably weren't clipping at the moderate levels one would encounter in a planetarium (lots lower than a live rock band, for example). And anyway, both mics would not clip at exactly the same time in every instance. But if he was running them into a mic input (rather than a line level input, as suggested in the instructions for that mic/module combo) then he might have overloaded the mic preamps. That would show up as some sort of anomaly in the waveform, but might have been much lower than 0dBFS depending on the configuration of the recorder. It still strikes me as odd, though, because some of the clicks are not at program peaks. For example, at about 28.707 there is a click with a level of about -5dB, but then after the click the level continues to increase to nearly -3dB without any further clipping. Then at about 28.746 there is a click with a level of about -6dB. So the clicks do not occur at a consistent level, and the waveform "voltage" sometimes increases after the time when the click occurs. Furthermore, the clicks occur at exactly the same time on both channels, even though the levels on the two channels are different. This isn't really what I'd expect if the electronics were clipping... I would expect that to happen at exactly the same level. Yet the clicks occur at exactly the same time on both channels, each and every time. Could it be some sort of malfunction of the AGC circuitry in the recorder? Seems unlikely... the AGC circuitry should have some sort of reasonable attack time and should not generate audible clicks when it operates. I really want to see the original file! ------------------ UPDATE: A pro who really knows what he's talking about assures me that if you import a WAV file into QTPro, and trim it to the size you want, then the "export" function can save a WAV format file with the data entirely unchanged from the original file. I don't use QTPro, so you'll have to look through your menus, settings, options, preferences, etc. and try to find the correct way to do this. Meanwhile, why don't you tell us the exact length (hrs/mins/secs) of the original file, and the exact file size (Bytes, kBytes, MBytes, or whatever). Then we can do the math and confirm what the sample rate and bit depth were. That will help us verify whether or not your editing procedure is changing bitrate or depth. ALSO: Are you running Windows or Mac platform? Last edited by Greg Miller; January 25th, 2011 at 05:44 PM. Reason: Updates

January 26th, 2011, 03:36 PM	#23
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Hi Micky, Thanks for sending the additional info and files. It's a lot to tackle, as this is getting deeper and deeper. But it's interesting. I'll at least start to reply now, and will post again later with more info. 1.) An electret condenser mic is a type of transducer that converts audio energy to electrical energy. All mics have two terminals where the signal comes out. Professional mics, with a "balanced" electrical connection, have two signal terminals, plus a separate ground/shield. Consumer electret mics are "unbalanced" and one of the signal terminals is exactly the same terminal as the ground/shield. In addition, there is a "hot" terminal which does two things: it accepts DC voltage ("plug in power") coming from the recorder or from the battery box, and it supplies the audio signal back to the recorder. Within certain limits, the signal voltage coming out of the mic is directly related to the acoustical energy going into the mic. More acoustical level produces more signal voltage. BUT there are some limits to this transfer function. For one thing, the physical reality of the mic limits the maximum physical excursion of the diaphragm. If, for example, the diaphragm can only move 0.01mm (which will be caused by some specific Sound Pressure Level) then a louder sound cannot move the diaphragm any farther than that. Another limiting factor is the DC voltage level being supplied to the mic (from the recorder or battery box). The mic output voltage cannot go any higher than the DC supply voltage (actually a bit less). So once the SPL reaches that level, the mic cannot produce any more output, even if the sound gets louder. For most "plug in power" condenser mics, the physical limit of the mic will be higher than the electrical limit (which is related to the DC voltage). Thus, you see specs for your mic that say the maximum level it can reproduce is 105dB SPL when powered by a typical recorder (which probably provides somewhere between 1.5 volts and 3 or 4 volts DC, depending on the model recorder); or the mic can reproduce 120dB SPL when powered by the battery box which provides 9 volts DC. So when you're recording anything that might be fairly loud, you definitely should use the battery box. (The upper limit for most "plug in power" mics is around 9 volts... you probably won't find battery boxes that have a higher voltage than that.) But now when the SPL gets loud, the voltage coming out of the mic can be pretty high... perhaps approaching 1 volt RMS. (I'm checking the specs for your specific mics.) That is too much level for most mic inputs to handle! That's why the mic's instructions say that you should always use the recorder's line input when using the battery box. And of course the line input does NOT have any "in line power" to worry about. 2.) Unless there's something really odd/bad about your present battery box, I don't think a different one would make the recordings any better. (Actually there are some purists who say that re-wiring the mic capsules, and using a custom battery box with the positive terminal grounded, rather than the usual negative ground, will provide cleaner audio. That's way far beyond the options that are available to you. Forget I mentioned it.) 3.) I was not really suggesting that you might have had the "plug in power" turned on, at the same time as the battery box. But yet, you might have. (see #4 below) In that case, it's hard to predict what might have happened. The output voltage from the mic might have risen higher than the recorder's "plug in power" voltage. Now, both the battery box and the recorder should have resistors (at least 1k ohms, maybe as high as 10k ohms) between the DC supply and the mic connector. Those resistors should hopefully protect against damage in a situation like this. But even if there was no damage per se, perhaps having the recorder's "plug in power" and the battery box both connected at the same time, might cause some unexpected behavior... such as strange clicks. Perhaps we'll never know for certain. 4.) You see by now that this is in the nature of a scientific investigation. It's hard to draw conclusions without knowing all the conditions of the experiment. And you've been very openly uncertain about what you did when you made this recording. (Was the gain high or low? Was "plug in power" on or off? Etc.) Obviously since we don't know these things for certain, we may never know for certain what caused the problem. One lesson here is that you should always be sure how everything is set and connected, and hopefully make a few notes for later reference! 5.) Your file was 1,707,370,028 Bytes / 2964 seconds. That's 576,036 Bytes/second = 4,608,286 bits/second. (96,000 samples/second) * (24 bits/sample) * (2 channels) = 4,608,000 bits/second So yes, your original recording was 96kHz/24bits, as you originally recalled. And that means that your previous "snip" operation did change the bit depth. So I definitely want to look at the original unchanged data, which hopefully you have sent today. ----- I think that answers most of the hypothetical questions so far. I think this is a good stopping point for this particular post. After I have time to check the new files, I'll post again with some more info. Last edited by Greg Miller; January 26th, 2011 at 04:32 PM.

January 27th, 2011, 02:18 PM	#24
Micky Hulse Major Player Join Date: Jul 2007 Location: Eugene, Oregon, USA Posts: 213	Greg... One word: WOW! THANKS so much for all the pro information! I am learning a ton. Awesome stuff! I definitely owe you one. Next time you are in Eugene I will buy you a beer! :) Thanks!!!!! Have an excellent day! Cheers, Micky :) __________________ Home: See *"Work"* :) Work: Canon XH A1, CS3/CS4/CS5/Final Cut Studio/Final Cut Express/Premiere Elements

February 1st, 2011, 12:09 PM	#29
Micky Hulse Major Player Join Date: Jul 2007 Location: Eugene, Oregon, USA Posts: 213	Ahhh, you know what, I just noticed that I can upload files! I guess you do have to have XX many posts before you can use this feature. :( __________________ Home: See *"Work"* :) Work: Canon XH A1, CS3/CS4/CS5/Final Cut Studio/Final Cut Express/Premiere Elements

January 25th, 2011, 11:43 AM	#16
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Thanks, Steve. Micky said he did use Audacity the last time around. Since the resulting file was 96kHz, and the R-09 only goes up to 48kHz, Audacity apparently changed the sample rate without Micky's conscious consent to do so. So my fear is that it may have made some other unknown changes, too... level, normalization, who knows what all? (And once the software has changed the samples, it will be harder for us to see what was actually recorded.) I'm looking for something essentially foolproof, so that he can send a short snip, without our worrying that the software has made changes in the actual sample values. Meanwhile, as a fallback, Micky can upload the entire 1GB file... but IMHO a nice unaltered snippet would be a lot easier to deal with.

January 25th, 2011, 12:58 PM	#18
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Micky, Ouch, I wish you had been more specific, earlier, about your recorder model number. It would have avoided some confusion on my part. However, I still think your use of Audacity did, in fact, change the file. You state that your original recording was 24bit/96kHz. However, the "snippet" you posted was only 16bit depth! So please, before we spend any more time on questionable files, post the original, unaltered, file!!! And post a timeline of where we can find some of the clicks (a cluster of at least a dozen clicks, close together, would be really helpful). No, I do not think your binaural mics recorded your ears popping! The anomalies in the file (actually I see abrupt jumps in level) occur exactly simultaneously on both channels. There is no chance in hades that both of your ears popped simultaneously, time after time after time. Forget that "ear popping" concept. Speaker pops? I'm not quite ready to rule that out, although I the more I look at the file, the less likely I am to name that as the culprit. Steve, by a strange coincidence, I actually worked as a tech at the "Albert Einstein Spacearium" which is the bureaucratic name of the planetarium in the National Air and Space Museum in Washington, DC, part of the Smithsonian Institution. When I was there, we did have some wretched Altec Lansing speaker cabs, which bottomed out drastically whenever the track contained any substantial amount of LF info... we had to roll off the LF effects to get a clean playback. In fact the track had been mixed at a studio with JBLs which were, of course, much cleaner. (It was embarassing... especially since the playback system in our IMAX theatre was so much better.) But that's not quite what a hear/see in Micky's files... it does not sound like speakers bottoming, and may or may not be in the playback system. OK, Micky, waiting for a complete original file from you...

January 25th, 2011, 01:35 PM	#20
Paul R Johnson Inner Circle Join Date: Nov 2005 Location: Lowestoft - UK Posts: 4,045	Just a thought - but did you use the battery module? The reason for asking is that if the bias voltage is supplied by the recorder, then the dynamic range of the mic is quite low - 105dB SPL (120 db when used with one of our battery modules). With so much bass, it's quite possible that the distortion are the mics itself - the recorder recording the distortion faithfully, which might also explain why the file, without being tinkered with, is at a modest level, but showing these clicks. The waveform, as mentioned hasn't flat topped, but is just spiky and rough - there's no audio peaks that cause it like snares or other percussive stuff - so could be the heavy bass components below 50Hz - which on a spectrum display seem very prominent.

January 29th, 2011, 04:10 PM	#25
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Micky, I have another installment for you. It includes 5 .gif files to illustrate what I'm talking about. I'm trying to find out how I can upload those files to the forum, so you can see them. As soon as I figure that out, I will post the stuff.

January 31st, 2011, 10:33 PM	#27
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Ah, OK. That was the only option I could find. The forum's FAQ says that, after I click "Reply" the reply page has a "Manage Attachments" area at the bottom of the page. I don't see it; can't find it. I thought either (1.) I was missing something obvious, or (2.) I hadn't generated enough posts yet to "earn" the right to post files. I EMailed the administrator about this question, but never got a reply. I will see about hosting them locally and then try linking to them. Film at eleven...

February 1st, 2011, 04:52 PM	#30
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Too bad I didn't see that posted anywhere in the FAQ. Maybe I need new glasses (if it's in there).