On Sun, 28 Dec 2008, Jamie Lokier wrote: > Bill Unruh wrote: >> 24 bit quantization error ( being at 135dB below the full signal-- >> ie completely and utterly inaudible > > Cumulative error in the (polyphase or not) digital filter arithmetic > is larger than sampling error. Still small, but how small depends on > how the filters are implemented. Sure. It is about 3-6 dB above that floor. Still inaudible. > >>> But the point is that the increased output sample rate allows >>> potentially better LPFs both in the polyphase FIR and in the >>> analogue domain after the DAC, compared with the fixed 2x rate, >>> which more than compensate at reducing alias band energy. >> >> The question is what you mean by better. If it is at amplitudes or >> frequencies which are inaudible, then it is irrelevant anyway. > > Ultrasonic physical acoustic mixing is a well known phenomenon which > is used deliberately sometimes to generate an audible modulated sound > in a limited space. I.e. it is real. That is one plausible reason > why "inaudible" frequencies are relevant to sound reproduction for the > very fussy. Sorry this is junk science. Yes, IM distortion of ultrasonic freq can be audible. Those ultrasonic frequencies have to be up above 100dB. No audio source has that kind of ultrasonic energy. And I think that last word is spelled with two z not two s. > > Amplitude is fair enough. > > I agree the higher sample rate, modified filters etc. are probably > irrelevent to all human listeners. I'm not that fussy myself. > > But they are a sensible trick if your technical objective is simply > making the highest quality sharp cut-off 96kHz 24-bit DAC you can. > > -- Jamie > -- William G. Unruh | Canadian Institute for| Tel: +1(604)822-3273 Physics&Astronomy | Advanced Research | Fax: +1(604)822-5324 UBC, Vancouver,BC | Program in Cosmology | unruh@xxxxxxxxxxxxxx Canada V6T 1Z1 | and Gravity | www.theory.physics.ubc.ca/ ------------------------------------------------------------------------------ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
