Re: [linux-audio-user] Piano feedback, again bundled

On Thu, Jan 23, 2003 at 07:27:15AM -0800, R Parker wrote: Very much so! If any signal exists at (for example) 30 kHz in the input to a 44 kHz A-D converter, that appears an audible signal at 14 kHz. An antialiasing filter has to be flat up to about 20kHz and cut off to a low level by 24kHz, as anything above 24k will alias to below 20k. That's a very tall order for a filter. Assuming a hearing limit of 20kHz again: At 96kHz sampling rate, the filter has to be flat to 20 kHz and cut off to a low level by 76kHz. That's a fairly easy filter to make! There are some signal processing issues too. I'm not an expert, but I believe it's quite difficult to do some types of digital filtering at frequencies getting close to half the sampling rate. -- Anahata anahata(a)treewind.co.uk Tel: 01638 720444 http://www.treewind.co.uk Mob: 07976 263827