ventilation noise ("Alain de Cheveigne'" )

Subject: ventilation noise
From:    "Alain de Cheveigne'"  <Alain.de.Cheveigne(at)IRCAM.FR>
Date:    Wed, 29 Mar 2000 22:04:43 +0100

We've just installed a new double-walled psychoacoustic booth and are
wondering about acceptable levels of ventilation noise.  After a first
change of ventilators the level in a 1/3 octave band at 100Hz is down to
about 40 dB SPL, as measured by a B&K sound meter (when ventilation is off
the meter fluctuates around 20 dB SPL).  We're wondering if we should
accept this as normal.  Has anyone made similar measures in a similar
booth?  Any insights are welcome.

Alain