Hallo, Hans-Christoph Steiner hat gesagt: // Hans-Christoph Steiner wrote: > Usually acoustic measurements are done with impulses, AFAIK. An > ideal impulse actually has all frequencies in it, so it's useful for > that kind of thing. Plus it's easy to differentiate between the > initial signal and the room effects just based on time.
Actually I think, engineers prefer to use frequency sweeps instead of pulses nowadays. The problem with pulses is, that they are hard to get right: You need a clean pulse and a very silent environment: The main problem with using Dirac pulses in an acoustical measurement is that as a result of their very short duration and finite amplitude, they contain very little energy, and measure- ment accuracy will be limited by the signal to noise ratio of the equipment used and of the system itself. While it is possible to use Dirac pulses reproduced by a loudspeaker in the con- trolled environment of an acoustics laboratory, this is all but infeasible in most real life situa- tions, e.g. for measuring a room or concert hall, where there will always be background noises of some sort. This is from Fons Adriaensen's LAC paper: http://lac.zkm.de/2006/papers/lac2006_fons_adriaensen_01.pdf Fons then explains sine sweeps as an alternative method: The advantage of using a sweep is that at any time we produce only a single frequency, and any distortion introduced will consist of the har- monics of that frequency only. If we use a rising frequency sweep, the harmonics will be gener- ated ahead of the same frequencies appearing in the signal. So after deconvolution, any dis- tortion will appear as spurious peaks in negative time in the impulse response, and most of it can then be edited out easily. This method's origin according to Fons is a paper by A. Farina: Angelo Farina. 2000. Simultanuous measurement of impulse response and distortion with a swept-sine technique. Audio Engineering Society Preprint 5093. It is implementes in Fons' ALIKI software, that he presented at LAC2006. Ciao -- Frank Barknecht _ ______footils.org_ __goto10.org__ _______________________________________________ [email protected] mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
