Feedback: Where did the 1 kHz tone come from?

[Daniel Rowan <dr@xxxxxxxxxxxxxxxx>]

Hi list

Many thanks to all those who responded to my question.  For those
interested, here is a summary of the feedback I had:

(1) The phenomenon is well documented.
(2) The audible f2-f1 DP is unlikely to arise from within the auditory
system and is measurable in the room using standard techniques.
(3) The most likely sources are (a) transducer distortion and/or (b)
non-linearities within the air, producing a DP with a highly position
specific amplitude.  The latter source has been exploited in commerical
audio equipment.  The impression I got is that the SPL of the primaries
required to produce a significant 1 kHz DP is much higher than implied
in the desciption my colleague here originally brought to my attention,
which is partly why we initially dismissed the transducer distortion.  I
had no idea the air was sufficiently non-linear at high SPLs to produce
audible intermodulation distortion!  Many thanks for all the feedback.

Best wishes

Daniel

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Daniel Rowan MSc
Research Student
Institute of Sound and Vibration Research
University of Southampton
University Road
Southampton SO17 1BJ
England, UK
Tel: 023 80594968
Email: dr@isvr.soton.ac.uk
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