Klarinet Archive - Posting 000054.txt from 1997/05

From: Roger Shilcock <roger.shilcock@-----.uk>
Subj: Re: Air : amount,speed,presure etc.
Date: Fri, 2 May 1997 18:17:10 -0400

On Thu, 1 May 1997, Jonathan Cohler wrote:

> Date: Thu, 1 May 1997 23:27:20 -0400
> From: Jonathan Cohler <cohler@-----.net>
> Reply-To: klarinet@-----.us
> To: klarinet@-----.us
> Subject: Re: Air : amount,speed,presure etc.
>
> Yossi wrote:
>
> >Does science ( or we the wind-players) know what air parameters influence
> >what sound parameters ?
> >
> >I mean:
> >
> >Is it the air speed which makes the ff ? or is it the amount of air
> >?
>
> This is actually a somewhat complicated question, and the answers given so
> far on the list are not really accurate.
>
> First, the quick answer is that perceived loudness of a sound is a function
> of the amplitudes and frequencies of all of the components of the sound as
> well as the quality of the listener's hearing.
>
> Some very simple and practical consequences of this are that high notes
> sound louder than low notes (at the same amplitude). This is why one must
> instantaneously reduce the blowing pressure when one makes a slur from a
> low note to a high note if one wants to make a seemless and even connection
> wherein both notes sound equal.
>
> Here is a bit of the physics of how this all works.
>
> People often confuse sound level and loudness, which are two totally
> separate things. Sound level is a measure of the intensity of sound
> pressure waves in the air. It is measured on a scale called decibels and
> is defined such that 0 decibels (dB) corresponds to a pressure of 20
> micropascals or millionths of a newton per square meter. In practice, this
> corresponds to an amount of sound that is just barely audible by the
> "average" ear in a "quiet" environment when listening to a frequency of
> 3000 Hz.
>
> Loudness is what a listener perceives. Therefore the scale for measuring
> loudness, called "phons", was developed based on averaging empirical
> results from tests of people with "normal" hearing. We humans can hear
> best between 2000 and 4000 Hz (because the ear canal has a resonance at
> approximately 3000 Hz), and our hearing gets less sensitive at both high
> and low frequencies.
>
> Therefore a loudness of 20 phons at 1000Hz corresponds to a sound level of
> 20dB, but 60dB at 16000Hz and 67dB at 31Hz. In other words, the sound
> level has to be much more intense at the high and low frequency extremes to
> be heard as the same loudness.
>
> Now we add the complication of the cochlear nerve and how we hear. To be
> as brief as possible, different areas of the cochlear nerve respond to
> different frequency ranges (called critical bands). In each of these
> frequency ranges there are "hair cells" that when excited transmit sound to
> the brain.
>
> Here's where it gets a bit tricky:
>
> A sound whose components lie all within one critical band uses the same set
> of hair cells to tell the brain how loud it is. Therefore, the loudness of
> this sound will depend only on the sound level.
>
> When a sound has components in multiple critical bands, however, more hair
> cells get in the action and the loudness is equal to the sum of the
> loudnesses in each critical band.
>
> What this means in practice on the clarinet is that since most of the
> overtones of a tone on the clarinet lie in separate critical bands, as we
> add overtones (by blowing harder) the sound gets louder. And,
> interestingly, *beyond a mezzo-piano, most of the increase in loudness is
> due to the addition of partials and NOT to the increase in amplitude of the
> fundamental*.
>
> Therefore, as one gets louder on the clarinet, the tone color also changes
> as the higher partials come into play.
>
> By the way, hearing changes as one ages and therefore so does loudness and
> tone quality perception. Older folks gradually lose sensitivity at higher
> frequencies.
>
>
> If you're interested in more information on this subject, a very good
> reference is "Music, Speech, Audio" by William J. Strong and George R.
> Plitnik, published by Soundprint in Provo, Utah (1992).
>
>
> -----------------------
> Jonathan Cohler
> cohler@-----.net
>
>
>
Doesn't the sounding length of the air column have a considerable effect
on clarinet tone production?
Roger SHilcock