holiday conundrum

["Richard J. Baker" <richard@xxxxxxxxxxxxxxxxxxx>]

A holiday conundrum courtesy of Sennheiser

The following passage is an extract from Sennheisser HD265 instructions. I
thought it would be an ideal quote for students to explain in an exam
situation!

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CORRECTION OF LOUDNESS DIFFUSION
In a dead or "anechoic" measurement chamber, a multitude of loudspeakers
independently emit noise-signals. In the middle zone of the measurement
chamber these different pieces of sound information meet and are
superimposed
in a "diffusion field", where it is no longer possible to tell from which
direction
each sound has come. These noises will be emitted one after the other at
third-
octave intervals, alternating over the loudspeakers, and then sent to the
headphones. A large number of researchers are at present assessing the
difference in volume between spatial noise and the sound in the headphones.

The aspired to ideal would be the same level of sound in the headphone as in
the
diffusion field. In practice, there is a greater atmospheric influence and
an improved
front-rear (external) detection system. To put it simply, the sound is
actually
occurring outside the head, is not limited to the space between the ears.
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TECHNICAL DATA
Frequency response      10Hz-30,000Hz (-3dB)
                                6Hz-35,000Hz (-10dB)
Acoustic principle      dynamic, sealed
Frequency curve         diffuse-field loudness equalization
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* Dr. Richard J. Baker
* University College London
* Dept. Phonetics & Linguistics
* Wolfson House,
* 4 Stephenson Way
* London NW1 2HE
Tel +44 (0)171 380 7403
Fax +44 (0)171 383 0752
http://www.phon.ucl.ac.uk/home/richard/home.htm

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