Summary of normal hearing (Nathan Weisz )

Subject: Summary of normal hearing
From:    Nathan Weisz  <nathan.weisz(at)UNI-KONSTANZ.DE>
Date:    Mon, 18 Apr 2005 11:46:41 +0200

Dear all,

Thanks for the many helpful answers concerning testing "normal hearing"
using SPL.
Since some people asked what answers I got and not all answers were sent
back to the list I've pasted the notes to this mail.

Best & thanks again,
Nathan


--------
#1
Please have a look at ISO 226 standard.....at least these values are
guilty
for free field.

#2
yes, the correspondance between dB SPL and HL is known:.
0dB HL = 15 dB SPL (250 Hz), 9dB SPL (500 Hz), 3dB SPL (1000 Hz), -3dB
SPL (2000 Hz), -4dB SPL (4000 Hz), 13dB SPL (8000 Hz).

#3
Normal hearing in dBHL is anything below 25 dB for adults (20 dB for
children).  If you're going to look at dB SPL, you have to just add the
correction factors for the following frequencies:

Hz        dB correction
125        45
250        27
500        13.5
1k        7.5
1.5        7.5
2k        9
3k        11.5
4k        12
6k        16
8k        15.5

#4
You can do the conversion from HL to SPL and figure out that way

#5
0.0002 dyne per cm sq

#6
There are ANSI standards for different headphones.

#7
Since "normal" is 0 dB HL, by definition, what you're really asking is
how to convert from HL to SPL.  Conversion factors are defined by
various standards, and they depend on the method of stimulus
presentation.  In the US, the relevant standard is ANSI S3.6.
 Internationally, there are different standards for different
presentation methods: ISO 389-1 for supra-aural headphones, ISO 389-2
for insert earphones, ISO 389-7 for soundfield, etc.  These standards
are outrageously expensive to buy, so see if you can find them in a
library somewhere.

#8
If I am not mistaken, 0 SPL is defined to be the threshold of normal
hearing.  There's probably a more standardized definition, but
basically near 0 SPL is "normal".  I presume I'll be corrected if I
remembered this wrong.