Zoom H2n Sound

[Dana Salsbury]

I simply have the Zoom sitting on a desk, running on AAs. The room is silent. Can anyone identify what might is generating this sound?

http://www.legacyhdv.com/noise.mov

Thank you!

[Rick Reineke]

What sound? It's usable Playback problem on the OPs end? I opened it in Sound Forge and do not hear (or see on the waveform) any major issues. What do you mean by "silent" ?

[Greg Miller]

I hear a tiny bit of noise, under the voice, near the end of the clip. There is not enough to identify.

Please post just a mono audio file that is longer, taken from your original audio recording, that has a significant amount of noise. Don't waste file size by including the video... that is entirely useless.

[Dana Salsbury]

Here is the wav file with the time codes where you can really hear it. My best guess is that the wiring in the Zoom is going out. Also I noticed that it's a straight Zoom H2. Again, no lav, running on batteries. I have the H2n in front of me on the desk.

http://legacyhdv.com/eric.wav
02:45-02:52
03:20-04:00
33.35-34.02

[Greg Miller]

• The first two examples are a high frequency buzz, and because I don't hear or see any on/off pulse modulation, I would suspect it's harmonics from a lower frequency source, rather than bleed from some digital signalling system. Thus, I would rule out things like cellphone interference.

The period is exactly 960 samples, which translates to a period of exactly 0.020 seconds, and a frequency of exactly 50 Hz. Thus, I'd suspect this is harmonics from some 50 Hz source. I see you're posting from the US, but if this was recorded in a country with 50 Hz power (e.g. the UK or Europe), I'd immediately suspect harmonics from the power distribution system. (Harmonics like this can be generated by solid-state lighting dimmers, or similar equipment.)

Another possibility is a monitor that's running with a vertical sweep rate of exactly 50 Hz, although I'd think that's rather slow for typical modern monitors. (60 Hz was common 15 years ago, but the frequency has generally gotten higher over the years.)


• The third example is different. It is not steady; it's pulsed. I hear more of this from 34:50.8 to 34:51.3, and in the following minutes of the file. This may well be interference from a cellphone, sending out RF to stay in contact with the cellular base. It may be some other form of RF communication, such as a Wi-Fi signal. It may even be crosstalk from a poorly shielded cable carrying some other form of digital signals.


• Then from 35:29.4 to 35:29.9, there is more steady-state low frequency noise. This spectrum is different from the buzz at the first two instances, there's a lot more lower-frequency content, and a lot less of the upper harmonics. It sounds more like a hum, rather than a buzz. Even so, the frequency is again very close to 50 Hz, so I'd suspect the same source that caused the earlier problem: power line noise, or vertical sweep from a video monitor.

• Also, observe the section from 08:10 to 08:45. I know I asked you not to send video... the file would be much too big. But can you tell us what was happening at that point in time? It sounds as if the talent is moving around, or possibly writing something... possibly manipulating something... possibly touching a keyboard, monitor, or some other electrical equipment. Whatever is happening there, the noise pickup changes from none, to very obvious, back to none, a few times. Can you check your video file and see what the talent is doing, what he's touching, where he's positioned, etc.?


•• Does the above give you any clues?


Finally, since there are two voices, I'm guessing that this was recorded with two separate mics. You posted a two-channel file. Yet the two tracks are exactly identical. Can you please explain, in detail, how this file was created? How many mics? Plugged into what? How and where was the mono mix created?

Thanks.

[Dana Salsbury]

Thank you Greg!

Evidence at the crime scene:
Two 20" 60 Hz monitors five feet away on in sleep mode
Mac Pro ten feet away in a closet on
Cell phone two feet away
My mic (Zoom H2n) two feet away
No nearby power lines
AC fan off
Six of those curly light bulbs on (brain tired)
No monitoring - using camera mounted shotgun and my mic as redundancy

The mono-mix was done by the Zoom itself as a menu option.

>observe the section from 08:10 to 08:45
He was writing notes from his cell phone which was 2-3 inches from the mic.

From what you said, it sounds like either cell phone interference, "crosstalk from a poorly shielded cable carrying some other form of digital signals" or both. The Zoom is old and road weary too. Thoughts?

[Greg Miller]

If he was playing with his cellphone from 8:10 to 8:45, then it appears the 50 Hz buzz is coming from the cellphone. Is it a smartphone? Was it on during the entire recording (perhaps used as a mini teleprompter)? If so, that's apparently where the buzz originates. Cellphones are usually "bad juju" where audio equipment is concerned.

(You say "AC fan off" but there is significant 120 Hz background throughout a lot of the file. Presumably this is a motor running somewhere... even if it was a refrigerator in another room. So there is certainly some 60 Hz equipment running. But that is not the source of the 50 Hz buzz.)

Please clearly and thoroughly explain what mics were used! You say the Zoom was "two feet away." Away from what???

Were you using only the internal mic(s) in the Zoom?

Were you using one or more external mics? If so, what kind? Connected with what sort of cable/connectors?

I really want to understand what you used for the sound source that was recorded on the Zoom... every tiny detail.

Once we know this info, we can figure out how the buzz got into the recorder, and how to avoid it in the future.

[Dana Salsbury]

I'm glad to blame the cell phone. That's an easy fix.

We did have the fan on before we started the interview officially. I'd forgotten about that.

He used a Zoom H2 with nothing plugged into it, and I used a Zoom H2n with nothing plugged into it. No lavs. The Zooms were two feet away from each other, as Eric and I were two feet away from each other. We only used the internal mics. Both mics were on and recording.

Can the buzz be from the cell phone too?

[Greg Miller]

If I understand you correctly, you initially had two separate recordings from two separate Zooms.

But the file you posted was a two-track file, with two identical tracks.

How did you get from two entirely separate recordings, to a single mixed recording?

[Dana Salsbury]

The Mono-mix function in the Zoom H2's menu creates just one wav file.

[Greg Miller]

Yeah, but you said you had TWO zooms sitting on the desk. And you posted ONE file.

So I don't understand about the file you posted.

Did it come from just ONE of the Zooms? Or did you take the two files, from the two Zooms, and mix those two files in post?

Sorry if I'm being dense here, I don't like to make any assumptions, I like every detail spelled out -- twice I guess. ;-)

[Dana Salsbury]

Thanks Greg. I haven't done any mixing. The Zoom H2n wav (the Zoom for my voice) was fine. I can upload it if you'd like. The one that you've listened to is entirely from the Zoom H2 (Eric's mic) with no lavs and nothing plugged in. It sat on the desk. Eric's cell phone was in his pocket once we started the interview.

[Rick Reineke]

The is after the fact but I'd advise of NOT using the H2's mono mode with only one input. It mixes in the noise of the unterminated channel, which can pick up RF spill and other extraneous sound. It would be better to record in the normal stereo mode and remove the unused channel in post.
Some recorders (like the Tascam DR40) have a single channel/file mono mode where this would be not an issue.
One could try Noise Reduction on the current issue or replace/overwrite good 'room tone' in pauses to make it less noticeable. An expander processor may help as well, attenuating the BG noise in those pauses.

[Greg Miller]

Rick,

I was wondering about exactly the same thing... mixing an open input into the final file. That's why I repeatedly asked what mic(s) he had used, and how he had arrived at the mixed-down file. (BTW, I think Zoom is pretty stupid to mix down to a stereo file with identical channels. Why not mix down to a single mono file, and use half as much memory?)

But the OP says he's using the Zoom's internal mics. So in that case, wouldn't he be mixing together the two internal mics, into one mono mix? Nothing would be unterminated.

[Rick Reineke]

So in that case, wouldn't he be mixing together the two internal mics, into one mono mix? Nothing would be unterminated
Right you are Greg! I was thinking "external input" Duh..
Could it be some kind of artifact from Zoom's mono mode summing architecture?

However my comment does still apply to the external input scenario.