OT:How good is camcorder audio?

riredale wrote on 7/16/2002, 5:37 PM
Sorry for straying a bit, but I've been working with the audio volume controls in VV, and I notice that my TRV-8 camcorder can never get any quieter than about -45db on the scale. I recall from earlier days that LPs and cassettes could do about -50db, and DolbyB added 10db to that. In addition, my understanding is that 16bit audio should have a floor of about -96db (6db per bit). So my question is whether -45db is good or terrible.

The funny thing is that my live choir recordings sound terrific, and I almost never notice the camcorder noise. I am assuming that camcorder audio circuits have some sort of slow-acting dynamic range adjustment, probably combined with some kind of curve at the top to prevent any hard clipping. Is this true?

Finally, I bought the little Sony external mike (MS908C), which according to various web reports is a decent mike, especially for the money. Once again, the best it can do is produce a noise floor also at -45db on the volume scale. The character of the noise is different, however; rather than motor noise it creates what sounds pretty much like white noise. All things being equal, this kind of noise would probably be much less obvious.

I recall that there are various ways of weighting noise, in an attempt to match the response curve of the human ear. How does this affect any of the above comments?

Comments

kkolbo wrote on 7/16/2002, 9:48 PM
What is probably happening is the auto-gain feature of the camcorder is struggling to find some audio in the quiet parts. When it reaches maximum gain, because there is no audio to get, it may have a -45db noise. That is one of the reasons pro cameras have manual gain and if they have an auto feature we turn it off. The TRV-8 is a consumer camera and I do not believe you can turn off the auto-gain.

BTW, if it sounds OK to you then it is fine. What you hear is more important than the specs in something like this. You need to be happy with your videos.

K
seeker wrote on 7/16/2002, 9:51 PM
Richard,

I haven't seen any reviews of camcorders that gave noise levels for the audio. I checked the manual that came with my Sony DCR-TRV510 NTSC Digital8, and its audio specification section said only, "Audio Recording System, Rotary heads, PCM system Quantization: 12 bits (Fs 32 kHz, stereo 1, stereo 2), 16 bits (Fs 48 kHz, stereo)."

On-camera mics typically do pick up motor noise and tape transport noise as well, and are susceptible to wind noise in their grates. This -45db thing may not be a serious problem, because the ambient noise in typical video taking situations is not low, as it would be in an audio recording studio.

I too am surprised that your external MS908C also had -45db, because eliminating the motor noise and tape transport noise should have made a significant difference. I suggest you take your camcorder and a fresh tape down to an electronics store and try out several external mics, and take a little footage of each mic itself (to identify it for later reference) and do an audio annotation as well. Then observe the taken noise levels for the various mics as best you can. Depending on how long you have had it, you might be able to return your MS908C and apply that purchase toward a better performing mic.

I won't comment on the human ear response curves, as I know very little about that. I have a lot of video footage that has serious ambient noise problems and, in some, wind noise was a problem. Even when I was using the built-in mic, ambient noise frequently swamped the motor/transport noise. I plan to use Sonic Foundry's Noise Reduction 2.0 DirectX plug-in to try to reduce my noise problems.

I am using the Sony smart-shoe-mounted ECM-HS1 zoom electret condenser microphone. Its sound quality is not excellent, but it is a significant improvement over the built-in mic. It is a foam-covered shotgun mic. The smart shoe feature lets the shotgun mic zoom to fit the zoom setting of the lens. That works fairly well. I think I will eventually get a better mic or mics, and maybe shoot for true stereo sound pickup.

-- Burton --
stepfour wrote on 7/16/2002, 10:53 PM
I bought one of those Sony MS908C on camera mic's, too, and was also disappointed with its abilities. I returned it and ultimately got a Sennheiser MKE300 directional mic. Great mic. Very happy with it. It's mono, but I do weddings and events so stereo sound is really not that important. Later I might invest in a high-quality stereo mic so I can have one on hand. For now the MKE300 is king.
riredale wrote on 7/17/2002, 12:47 AM
Thanks to all for the comments; kkolbo, I think you're right about the auto-gain on my camcorder, in fact, I think I can hear it boosting the gain over the span of several seconds in extremely quiet conditions. I think we are all so used to the horrible compression used by network TV that the modest "pumping" used by consumer cameras sounds pretty good by comparison. The microphone(s) built into the TRV-8 are surprisingly good to my 52-year-old ears, and I suspect that the diligent engineers at Sony did some sort of motor noise envelope study and then tried to mask the worst of it with notch filtering.

For those of you that use pro or semipro gear: do those mikes really have the kind of enormous dymanic range to be able to get down to the -96db noise floor of 16-bit audio? Do professional studios routinely deal with this kind of dynamic range?
snicholshms wrote on 7/17/2002, 1:18 AM
I'm not a recording engineer...just know what I like when I hear it. I too couldn't stand the onboard camera mic so I bought a Beachtek Dual XLR adaptor (www.beachtek.com) for my JVC DVM-90 camera. They have one for Sony cams.
Also bought two Shure unidirectional mics from a music store for about $50 each...now I get GREAT sound!
Also got a $15.00 35mm camera flash shoe attachment brace that screws into the tripod hole on the bottom of the JVC cam. It has a handle that also allows better stability when filming AND it isolates the mic away from the camera...NO "noise"!
One mic is mounted on the brace and another can be used for interviews when the camera is on a tripod and I need to be the interviewer on camera.
I'm 53, kid! Ha!