Subject: Re: swept sine accuracy From: Jaime Undurraga Lucero <jaime.undurraga@xxxxxxxx> Date: Fri, 6 Mar 2009 12:03:09 +0100 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--0003255760b2e9a6f10464713ab1 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable This is an interesting paper about sweeps SWEN M=DCLLER, PAULO MASSARANI, Transfer-Function Measurement with Sweeps, DIRECTOR=92S CUT INCLUDING PREVIOUSLY UNRELEASED MATERIAL http://saturn5.com/~jwb/mueller.pdf best regards, jaime undurraga On Fri, Mar 6, 2009 at 11:49 AM, Jose Almagro <luegotelodigo@xxxxxxxx>wrot= e: > I agree that the main problem is SNR/INR, anyway there's a comparison > between short sweeps average and long sweeps I think it's written by Fari= na > but I'm not sure, maybe by M=FCller. > > Best regards > > 2009/3/6 Piotr Majdak <piotr@xxxxxxxx> > >> Dear James, >> >> If you have noise in the system (=3Droom) then the sweep duration primar= ly >> depends on the signal-to-noise ratio (SNR) you want to achieve. This is >> because usually, the maximum amplitude of the loudspeaker is limited. >> Further, for exponential sweeps, the SNR may depend on frequency, f.e., = it's >> pink if noise is white. >> >> For example, we use sweeps with at least 1.5-s duration for measurements >> in a sound chamber (18 dB noise) to achieve an SNR of 60 dB. For such lo= ng >> sweeps, the frequency smearing is negligible. >> >> However, I do not have a theoretical result... >> >> br, Piotr Majdak >> >> >> James W. Beauchamp wrote: >> >>> Guys, >>> >>> This is a not strictly an auditory question, but it could be >>> useful for people doing acoustic measurements. If you use a >>> swept sine wave to measure the frequency response of a linear >>> system, what is the limitation on the speed of the sweep in >>> terms of how accurate the result would be? I imagine it has >>> something to do with how smooth the actual frequency response is. If it >>> has some pronounced bumps, they could be smoothed >>> out if the sweep is too fast. >>> >>> In practice, you could sweep at some arbitrary rate, and then >>> slow it by a factor of two, and if the result is the same >>> (within an acceptable tolerance) you could say that you've >>> converged on the solution. >>> >>> But I'd like to have a theoretical result. >>> >>> Jim Beauchamp >>> Univ. of Illinois at Urbana-Champaign >>> >>> >> > --=20 Jaime Undurraga, Eng PhD Student ExpORL, Dept. Neurosciences Katholieke Universiteit Leuven Herestraat 49, bus 721 3000 Leuven, Belgium Tel: +32 16 330485 Fax: +32 16 330486 _____________________________________________________ http://jaime.undurraga.googlepages.com --0003255760b2e9a6f10464713ab1 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable This is an interesting paper about sweeps <br>SWEN M=DCLLER, PAULO MASSARAN= I, Transfer-Function Measurement with Sweeps, DIRECTOR=92S CUT INCLUDING PR= EVIOUSLY UNRELEASED MATERIAL<br><a href=3D"http://saturn5.com/~jwb/mueller.= pdf">http://saturn5.com/~jwb/mueller.pdf</a><br> best regards,<br>jaime undurraga<br><br><div class=3D"gmail_quote">On Fri, = Mar 6, 2009 at 11:49 AM, Jose Almagro <span dir=3D"ltr"><<a href=3D"mail= to:luegotelodigo@xxxxxxxx">luegotelodigo@xxxxxxxx</a>></span> wrote:<b= r> <blockquote class=3D"gmail_quote" style=3D"border-left: 1px solid rgb(204, = 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div><div></div><= div class=3D"h5"><div>=A0=A0=A0 I agree that the main problem is SNR/INR, a= nyway there's a comparison between short sweeps average and long sweeps= I think it's written by Farina but I'm not sure, maybe by M=FCller= .</div> <div>=A0</div> <div>=A0=A0=A0 Best regards<br><br></div> <div class=3D"gmail_quote">2009/3/6 Piotr Majdak <span dir=3D"ltr"><<a h= ref=3D"mailto:piotr@xxxxxxxx" target=3D"_blank">piotr@xxxxxxxx</a>><= /span><br> <blockquote class=3D"gmail_quote" style=3D"border-left: 1px solid rgb(204, = 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">Dear James,<br><b= r>If you have noise in the system (=3Droom) then the sweep duration primarl= y depends on the signal-to-noise ratio (SNR) you want to achieve. This is b= ecause usually, the maximum amplitude of the loudspeaker is limited. Furthe= r, for exponential sweeps, the SNR may depend on frequency, f.e., it's = pink if noise is white.<br> <br>For example, we use sweeps with at least 1.5-s duration for measurement= s in a sound chamber (18 dB noise) to achieve an SNR of 60 dB. For such lon= g sweeps, the frequency smearing is negligible.<br><br>However, I do not ha= ve a theoretical result...<br> <br>br, Piotr Majdak=20 <div> <div></div> <div><br><br>James W. Beauchamp wrote:<br> <blockquote class=3D"gmail_quote" style=3D"border-left: 1px solid rgb(204, = 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">Guys,<br><br>This= is a not strictly an auditory question, but it could be<br>useful for peop= le doing acoustic measurements. If you use a<br> swept sine wave to measure the frequency response of a linear<br>system, wh= at is the limitation on the speed of the sweep in<br>terms of how accurate = the result would be? I imagine it has<br>something to do with how smooth th= e actual frequency response is. If it has some pronounced bumps, they could= be smoothed<br> out if the sweep is too fast.<br><br>In practice, you could sweep at some a= rbitrary rate, and then<br>slow it by a factor of two, and if the result is= the same<br>(within an acceptable tolerance) you could say that you've= <br> converged on the solution.<br><br>But I'd like to have a theoretical re= sult.<br><br>Jim Beauchamp<br>Univ. of Illinois at Urbana-Champaign<br>=A0<= br></blockquote></div></div></blockquote></div><br> </div></div></blockquote></div><br><br clear=3D"all"><br>-- <br>Jaime Undur= raga, Eng<br>PhD Student<br>ExpORL, Dept. Neurosciences <br>Katholieke Univ= ersiteit Leuven <br>Herestraat 49, bus 721<br>3000 Leuven, Belgium<br>Tel: = =A0+32 16 330485<br> Fax: +32 16 330486<br>_____________________________________________________= <br><a href=3D"http://jaime.undurraga.googlepages.com">http://jaime.undurra= ga.googlepages.com</a><br> --0003255760b2e9a6f10464713ab1--