Subject: Re: Music Transmission Index? From: Christine Rankovic <rankovic(at)articulation.com> Date: Tue, 11 Jan 2005 09:43:03 -0500Michael and List Readers: I don't know of an index for music that is analogous to the AI. A "music transmission index," (presumably, this would predict the perceived fidelity of music from acoustical measurements) would be useful in many applications, particularly in my area of interest which is hearing aids. I would greatly appreciate any references to review papers or standards describing metrics used to quantify fidelity of equipment that transmits music because I am not familiar with the fidelity literature, other than for speech and hearing aids. The articulation index rates the communication pathway on how well it transmits speech sounds. An AI for music would indicate the quality of the listening experience over a music transmission pathway, with the "golden ear" listeners approving of AI = 1.0. Perceiving/recognizing/enjoying music requires finer hearing ability than needed for recognizing speech; even so, the AI calculation [Fletcher, H. and Galt, R.H., 1950, Journal of the Acoustical Society of America 22: 89-151] may provide a useful starting point and framework for devising a music index. This is because the AI includes detection thresholds, loudness, critical bands, and other psychoacoustic constants assembled in such a way so as to determine the "amount" of speech "received," and a music index would need these constants too (in some form). Then there would be more psychoacoustic data to account for the greater demands on the ear required to process the music signal. Maybe it wouldn't be so hard to construct an index for music. Experimental work is required. Perhaps, the first step is to see how well the AI in its present form can predict listeners' ratings of fidelity for conditions where music is filtered or noise-masked. These are the conditions for which the AI was designed. (Does anyone know of existing data like these?) We already know that the "speech" AI is deficient for music because the AI is limited to the frequency range 180-8000 Hz and music needs a wider range. Even though there are a multitude of other difficult problems with applying the AI to music-for example, how to quantify music to incorporated it into the calculation (in the case of speech, the AI uses the long-term average spectrum and level-distribution of a sample of connected speech)-I believe constructing a music index is possible. The folks who developed the original articulation index solved these problems for speech, and that seems impossible to me even today. Is anyone interested in or involved with music fidelity metrics? Please send comments! Christine Rankovic Articulation Incorporated Newton, MA USA ----- Original Message ----- From: "Büchler Michael" <Michael.Buechler(at)USZ.CH> To: <AUDITORY(at)LISTS.MCGILL.CA> Sent: Monday, January 03, 2005 4:09 AM Subject: Music Transmission Index? Dear List Recent postings about the AI, STI and SII made me wonder if there exists something like a "Music Transmission Index". Any comments and advice regarding previous work and references would be greatly appreciated. Regards Michael -------------------------------- Michael Buechler PhD University Hospital ENT Department Frauenklinikstr. 24 CH-8091 Zurich / Switzerland --------------------------------