power(10,db/10). I'm not sure which one is more efficient. Any takers?
Cheers, Ross.
Neven MacEwan wrote:
>Ross > >exp() is a natural log, ie exponential of e, not exponential of 10 >Delphi has a log10 function but no Exp10 function I can see so >To do this you do use > >exp(db/10*ln(10)) > >HTH > >Neven >----- Original Message ----- >From: "Ross Levis" <[EMAIL PROTECTED]> >To: "Multiple recipients of list delphi" <[EMAIL PROTECTED]> >Sent: Thursday, March 06, 2003 4:54 PM >Subject: Re: [DUG]: db calculation > > > > >>Hi >> >>This formula doesn't seem to work. The 20 should be 10 as Neven pointed >>out but I believe a -3db reduction should take 65535 to 32767 but it's >>not close. Any ideas? >> >>Cheers, >>Ross. >> >>Nello Sestini wrote: >> >> >> >>> (db/20) >>>P1 = P2 e >>> >>>i.e. P1 = P2*exp(db/20) >>> >>> >>>not sure if this is what you are after >>>(and hope i haven't made some stupid mistake) >>> >>> >>> >>>-ns >>>http://www.roserox.co.th >>> >>> >>>----- Original Message ----- >>>From: "Ross Levis" <[EMAIL PROTECTED] >>><mailto:[EMAIL PROTECTED]>> >>>To: "Multiple recipients of list delphi" <[EMAIL PROTECTED] >>><mailto:[EMAIL PROTECTED]>> >>>Sent: Thursday, March 06, 2003 09:57 >>>Subject: [DUG]: db calculation >>> >>> >>> >>>>Here's a maths question for you. I've never been that good at maths, >>>>particularly logarithms >>>> >>>>Does anyone know the formula to alter an integer value by a particular >>>>db value. >>>> >>>>I'm working on an audio app and I need to alter the volume by a >>>>particular db setting. The volume can be anywhere in the range 0 >>>>(silent) to 65535 (maximum). >>>> >>>>I know that db = 20 log (P1/P2) though I've also seen the 20 at 10. >>>> >>>> >>>How >>> >>> >>>>do I get P1 (or is it P2) to the left of the equation. >>>> >>>>Thanks, >>>>Ross Levis. >>>> >>>> >>>> >>>> >>-------------------------------------------------------------------------- >> >> >- > > >>>> New Zealand Delphi Users group - Delphi List - >>>> >>>> >>>[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> >>> >>> >>>> Website: http://www.delphi.org.nz >>>>To UnSub, send email to: [EMAIL PROTECTED] >>>> >>>> >>><mailto:[EMAIL PROTECTED]> >>> >>> >>>>with body of "unsubscribe delphi" >>>>Web Archive at: http://www.mail-archive.com/delphi%40delphi.org.nz/ >>>> >>>> >>>> >> >>-------------------------------------------------------------------------- >> >> >- > > >> New Zealand Delphi Users group - Delphi List - [EMAIL PROTECTED] >> Website: http://www.delphi.org.nz >>To UnSub, send email to: [EMAIL PROTECTED] >>with body of "unsubscribe delphi" >>Web Archive at: http://www.mail-archive.com/delphi%40delphi.org.nz/ >> >> >> >> > >--------------------------------------------------------------------------- > New Zealand Delphi Users group - Delphi List - [EMAIL PROTECTED] > Website: http://www.delphi.org.nz >To UnSub, send email to: [EMAIL PROTECTED] >with body of "unsubscribe delphi" >Web Archive at: http://www.mail-archive.com/delphi%40delphi.org.nz/ > > >
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