HV20 Audio Noise Data

[Don Palomaki]

Got my hands on a HV20 for a few hours. Did some informal tests on audio noise levels at the external mic jack. The test was insert a dummy mini-phone plug so internal mic was disconnected, and external mic input was floating (not grounded or terminated, tis is a worst case because the metal in the plug could act as an antenna, but any effect was small if present).

I tried 6 tests. Camcorder was set to SD video, P mode, 16-bit audio, battey powered, and firewire capture into WAV files. I changed the MIC ATT setting and audio gain for each test. The test conditions were:

Audio AGC on, with and without MIC ATT.
Manual gain, green bar at about -12, with and without MIC ATT
Manual gain at max, with and without MIC ATT.
Looked at left and right channels.

Used Adobe Audition to check sound. I looked at the average RMS noise level relative to max allowable sine wave record level, and at the frequency spectrum of the noise. The Results for noise level averaging left and right channel:

AGC, ATT off: -56 dB
AGC, ATT on: -64 dB
-12 gain, ATT off: -61 dB
-12 gain, ATT on: -69 dB
Max gain, ATT off: -49 dB
Max gain, ATT on: -57 dB

In all cases the noise spectrum was fairly flat, with slight peaks at precisely 8 and 16 kHz. The noise level in the left channel averaged slightly lower (about 2 dB) than the right channel.

That the noise level increased by 12 dB at the maximum manual gain setting is no surprise, and indicates that the audio noise is mainly from circuits that are ahead of the gain controls.

While this is a good bit noisier than the XH-A1 for example, overall it is not bad for a consumer camcorder. It does show that using a good external mic with fairly high output is a benefit in terms of signal to noise.
See: http://www.dvinfo.net/conf/showthread.php?t=89879 for data on the XH-A1

I did not test the built-in mic because ambient noise around my work station is just too high to get meaningful test results.