Wireless audio - noisey!

[Greg Miller]

Michael,

I hope you're recovering from your crash last week!

I am recovering from a failing C:\ drive here. Chkdsk took 24 hours to fix the data structure on the original drive. I started to clone the drive yesterday, only to have power go off (900+ homes) for five hours. (The UPS kept the machine running for about 30 minutes, but it died before the drive was cloned.)

I finally finished up last night around midnight, and downloaded your file this morning.

Well...

That clipping is pretty severe. You certainly want to avoid that in the future. Feeding a lower level to the camera might prevent that... if I were you I'd try a few tests before the next actual event.

As far as using software that will implement downward expansion, to counteract the AGC in the recording... I'm afraid I think that's going to be impossible. In many instances, there is room noise at a relatively low level for a while, then the AGC ramps it up. There's no way for software to automatically know that the increasing level is noise which should remain at a low level... after all it might be some desired audio that causes the level to increase. So I'm sorry, but I think if you wanted to repair the damage caused by the AGC, you'd have to do it manually... a very tedious prospect.

You might be able to use software to automatically get rid of the high frequency interference. There are two approaches to that.

The interference is odd, in that it's a constantly changing frequency which comes down as low as 6 kHz.

You could just run all the audio through a fairly sharp high-cut filter. However, that leaves the voice sounding obviously filtered.

Or you could split the track into two frequency bands (separated around 6 kHz), and use some aggressive downward expansion on the HF band, to get rid of all HF information except during desired audio (speech). However, the AGC pumping on the original track works against this approach. So you'd have to manually fix all the levels (as described above) before you could use this filtering technique.

And, incidentally, there seems to be some sort of expansion already used on this track! Listen to the section from 4:06 to 4:20. Right around 4:08 the level comes up for about two seconds, for no obvious reason. The same thing happens again from 4:12.5 to 4:14.5, and again from 4:17.0 to 4:17.5.

So you have at least four obvious issues with this track: clipping, HF interference, AGC, and some sort of expansion. Not an easy one to fix. If I were an archivist, and this were a recording of a presidential inauguration, it might be worth the effort...

By all means, you want to run some tests, and listen very closely, before your next recording event.

[Harry Simpson]

Originally Posted by Chris Harding

Just avoid any mixer feeds...most operators have no idea what they are doing and you are at their complete mercy!!!

Chris

Never heard this before but am really starting to believe it!! The "sound dudes" aren't always top notch. I have been getting feeds out into a ZOOM H4n XLR input and monitor with headphones and that works but I've had to ask for "a little more" or "a little less" during sound check to even get that right.....

[Steve House]

Originally Posted by Harry Simpson

Never heard this before but am really starting to believe it!! The "sound dudes" aren't always top notch. I have been getting feeds out into a ZOOM H4n XLR input and monitor with headphones and that works but I've had to ask for "a little more" or "a little less" during sound check to even get that right.....

Remember too, even if they know what they're doing, their mix might not be suitable for recording. There can be entire instruments such as drum kits or guitar cabinets that are completely unmic'ed. The 'sound dude' is going to mix what he thinks sounds right to the FOH audience, which is completely different from the mix you need.

[Harry Simpson]

Steve you are correct - i've learned that (probably here from you) so I usually have a RODE SVM mic on a bracket connected to my 5Dmk2 and use it for syncing mostly but may be a good blend to the board track to get more ambient "live" sound to add to the project. Is that what you do?

[Jim Snow]

Originally Posted by Steve House

Remember too, even if they know what they're doing, their mix might not be suitable for recording. There can be entire instruments such as drum kits or guitar cabinets that are completely unmic'ed. The 'sound dude' is going to mix what he thinks sounds right to the FOH audience, which is completely different from the mix you need.

I have found that to be very true. If the sound engineer is mixing a band for the PA with a live audience, the board feed is almost always useless for recording purposes. At a live performance, the audience hears both the PA and the actual sound from the band. The sound engineer mixes for the right balance for the live audience which usually isn't a good recording mix. Some instruments need more boosting than others with a live performance. It is usually best to use recorder(s) strategically placed for the audio source for a live band performance.