From: "Richard Plourde" <richardplourde@m...>
Date: Thu Jan 11, 2001 2:57 pm
Subject: Vocal frequency range
Was: Re: Structure-born noise
--- In acoustics@e????ups.com, Stephen Foster <oncourse@i...> wrote:
Plourde:
> >Yes, it could reduce the amplification of stage
> >vibration. But so much of sound reinforcement does
> >not require the microphone pickup of low frequencies.
> >For human voice, for example, there's no reason that
> >I can think of for not using a sharp high-pass filter
> >at 100Hz or even a bit higher.
>
> Gosh... hate to disagree, but as a vocalist and engineer,
> I know that a great deal of my vocal sound is generated
> below 100 cycles.
In reading your message, it appears that you lump in
some instruments with "vocal sound." I was speaking
only of human voice. (And, of course, I'd expect some
exceptions -- an operatic basso profundo might very
well have learned to get below 100Hz -- although I
have no confirming data.)
I'm working from memory here (both text-book memory and
some 20 year old experimental stuff), but, as I recall,
the male formant region is typically in the 120/130Hz
region, the female formant 160/170Hz. I don't see how
it's possible to go lower than that, and my spectral
measurements (not with singers, granted) didn't show
any energy below the formant region.
However, since neither my experiments, nor available
data, included trained singing voices, I can't say
with any confidence that lower frequency output does
not occur. (I suppose that anyone with access to
sound-booth vocals could feed some vocal tracks
through a spectrum analyzer. My general rule is,
if it's important and you aren't sure, make a
measurement; it gets you farther than talking does.)
But, of course, get outside of human vocals, (e.g.
"live sound" from all the sources on the stage) and
all bets are off.
> I can understand not using very low freqs, like
> maybe 50 cycles and under, for live sound, but
> that's only if you have either an inadequate sound
> system or a scared engineer (or both).
In the past, I've worked in the loudspeaker business
(not amateur -- brand-name companies) doing mostly
research. Human perceptions are quite odd -- not at
all what you'd deduce from such things as "equal
loudness contours." A strange thing occurs in the
difference between harmonic structure (most instru-
ments) and enharmonic structure (e.g. drums.) With
harmonic structures, the human brain seems to "fill
in" (in a fairly satisfactory way) missing funda-
mentals. With enharmonic structures, when you lose
a frequency range (for example, low bass), you end
up with something that "sounds different."
With training, anyone can learn to distinguish almost
anything. (For example, while most people simply
cannot determine the direction from which a low
bass note comes, sailors can.) But, with naive
(not an insult) listeners, it's possible to lop off
the bottom end of a piano recording (with the pianist
playing low notes) at 50Hz or so, and get a descriptive
response of "well, I guess it's a little bit different,
but not much," while with kick drum, consistently
people will report a 50Hz cutoff as "it's completely
different" compared to, say, a 20Hz cutoff. At home,
I have a system that goes down to ~25Hz with low
distortion; I actually get annoyed when I hear
reproduction that doesn't cover the bottom octave.
(This is, of course, a completely different issue
from that of high intensity low frequency production,
where the entire human body becomes involved, and
we're not just talking about how the ear/brain
apparatus works.)
> You can't fix a midrange problem with midrange EQ
> if the problem is being caused in the low end. If
> I caught a live engineer high-passing my vocals (or
> the bass, kick, or guitars) like that I'd replace
> him if he insisted on continuing the practice.
You'll get zero-argument from me with regard to the
instruments -- particularly for kick drum or for
instances where 'feel' (very high intensity) becomes
a factor. (If you want vision to blur, and it doesn't
blur because you cut the bass, then you've failed.)
I skeptically defer to your experience with regard to
vocals. (Hey, you do "in the field" stuff; I've
only done research -- but I'd still like to see some
vocal spectra.)
Also, perception is affected directly by sound
intensity. (The explanations of how "loudness
controls" somehow "compensate" for playback at lower
sound levels are utterly bogus -- soft sounds different
from loud; you're only choices are how to make the
soft sound satisfactory to the listener, not how to
make it "nearly the same.") There's a lot of energy
below 100Hz -- if you get rid of it, you can't
compensate elsewhere.
>
> As a matter of fact, the best engineers actually
> cut a hole in the drum EQ at exactly 100 cycles to
> fit the vocal into.
Yup -- that's sounds like a good idea. It would
help avoid problems of masking.
-R