Topic: Strange waveform disbalance

[piktstevs]

It’s not the first time I can’t believe my eyes when looking at waveforms of my recordings and actually I can live with that, but finally I decided to ask for explanation. Because it became even more curious when I completely changed my recording equipment and got the same mystery.

So the essence of this mystery is that visual disbalance of channels does not correspond to sonic balance. This is an example (downsampled excerpt in FLAC): http://www.mediafire.com/download/t41f84t199z4tvz/Excerpt.flac . The recording made with SP-CMC-8 (hc, low sens mod) > SP-SPSB-11 (no bass roll-off) > Tascam DR-40 [mic-in, WAV 24-bit/48 kHz].

Visually the waveform of the left channel is notably weaker, but the recording sounds quite balanced. How can this be? Thank you very much for any ideas.

[Len Moskowitz (Core Sound)]

Have a look at the frequency domain representation of this waveform. You might find the answer there.

[bombdiggity]

I'm not sure what may have caused it but your left channel is averaging 4dB lower than your right.  IMO that is too much.  I hear the left channel as weak. 

Going into "Amplitude statistics" in Audition (or Cool Edit) will give you some indicator of the signal strength/characteristics

Your original was:

                 Left   Right
Min Sample Value:   -21478   -29601
Max Sample Value:   18898   29153
Peak Amplitude:   -3.67 dB   -.89 dB
Possibly Clipped:   0   0
DC Offset:      .041    .042
Minimum RMS Power:   -67.78 dB   -67.48 dB
Maximum RMS Power:   -12.78 dB   -7.46 dB
Average RMS Power:   -22.41 dB   -18.31 dB
Total RMS Power:   -21.08 dB   -16.7 dB
Actual Bit Depth:   16 Bits   16 Bits

I suspect it is a mic positioning issue relative to the sound source since you do have some stereo imaging/differences.  IMO the weaker (left) channel actually has better sound on it than the right channel.  It also appears you are consistently 4 samples or so out of phase (the left channel is leading the right).  That will make the results sound muddier than they should be.  That is usually an indication of positioning as well. 

Oddly in perceptual terms of the resulting sound the left channel being ahead in phase will offset at least some of its weaker level so aurally it may not seem quite as weak as it actually is. 

Aiming for getting the two channels to average roughly the same I hard limited the left to add 4 dB. 

That results in:

                 Left   Right
Min Sample Value:   -32392   -29601
Max Sample Value:   29577   29153
Peak Amplitude:      -.11 dB   -.89 dB
Possibly Clipped:   0   0
DC Offset:      .065    .042
Minimum RMS Power:   -63.78 dB   -67.48 dB
Maximum RMS Power:   -8.78 dB   -7.46 dB
Average RMS Power:   -18.41 dB   -18.31 dB
Total RMS Power:   -17.08 dB   -16.7 dB
Actual Bit Depth:   16 Bits   16 Bits

As I said I like the left better (it sounds cleaner/less reverb) so I would definitely bring it up and get them more balanced. 

You also have a pronounced DC offset here.  That is really unusual on a digital source and may indicate something is amiss in the chain (particularly if you always have the left weak and always have a DC offset).  You can correct the DC offset result in editing. 

I would also adjust the phase (move the entire left channel back 4 samples - in the 16bit realm as the measure will be different in 24 bit - before tracking/splitting) - unless of course you moved and the phase differential is a shifting target. 

[piktstevs]

Thank you for detailed answer. Got lots of information to study.

[nulldogmas]

Bombdiggity, how are you detecting the 4-samples out of phase problem? I have a couple of "waveform looks off-center, but it sounds centered" recordings that I'd like to go back to and check to see if this is the same cause, but when I zoom in to that level of detail it's tough for me to tell if the two channels are matching up.