Sharpness calculation (Jonathan Roberts )

Subject: Sharpness calculation
From:    Jonathan Roberts  <J.R.Roberts(at)LBORO.AC.UK>
Date:    Tue, 13 Jan 2004 13:39:34 -0000

I am interested in calculating metrics such as loudness and sharpness of short duration (~50ms),
impulsive sounds. From what I can gather, this involves taking a spectrum of the sound, transforming
it first into an excitation pattern and then to specific loudness; the area under the specific
loudness pattern is then proportional to the loudness of the sound and the weighted first moment of
the pattern is the sharpness. First of all, is my understanding correct? Secondly, I have heard of
different methods for calculating sharpness, such as the Zwicker and Aures methods, can anybody
explain the differences please?
Unfortunately we do not have the sound quality package for our acquisition software to calculate
these metrics but I have obtained MATLAB code from Aaron Hastings for calculating loudness according
to ISO 532B and DIN 45 631. Can the loudness pattern obtained using this method be used to calculate
sharpness? If so, is it a case of using the weighting factor, g, given in Fig 9.2 of
Psychoacoustics: Facts and Models and then calculating the weighted first moment of the pattern?
Finally, are there any implications when using these parameters with short duration, transient
sounds and, if so, are there more suitable models for these types of sounds?

Thanks in advance,

Jon Roberts