Re: [LAU] Sampling rates [WAS]: Re: jack/oversampling

On 03/16/2014 09:50 PM, Lorenzo Sutton wrote: i once talked to a bat researcher (no joke) who had a simple mod to a røde nt5 that would allow it to work reasonably well up to 30k. earthworks make special versions of their excellent microphones which are linear up to 50khz, for those who need it (or think they need it). in fact, most if not all microphones can do this but for additional filters added by the manufacturers to increase robustness in the presence of HF electromagnetic noise. the question is how linear they are up there, and whether the pickup pattern is still useful. all but the smallest capsules can be expected to become highly directional at HF. something like a DPA 4060 or a SH MKE-1 might be good experimental capsules for ultrasonics. most tweeters are easily capable of 30khz, and there are no major engineering obstacles to 50khz on-axis. the big issue is excessive beaming, both on the recording and playback side of things. i'd tend to agree with that statement, but there are very valid reasons to do it: * not all recordings are meant for humans to hear - if you are measuring something, you might appreciate results outside of human sensation. * not all recordings are meant to be heard in its original frequency range - talk to any bat enthusiast. seriously, what those guys do makes you itch to try 192khz and a microphone that is open "from dc to daylight", as the saying goes. * sometimes, preservation of information is extremely important. for instance, there are valid reasons to digitize old analog tapes at ridiculous rates (say, 384 kHz): doing so lets you record traces of the HF bias, which might help in eliminating wow and flutter artefacts more precisely than tracking the 50 or 60hz power grid hum. or there's a colleague from italy, david monacchi, who records sound scapes in soon-to-be-destroyed natural habitats - why would you limit yourself to 10 octaves if you can get 11, before the bulldozers arrive? (i once heard him lecture on one of his works, and indeed he was using sonograms to identify certain species of animals, many of which are capable of uttering ultrasonics.) there is still ongoing debate about indirect audibility of high frequency content via transients - i'm not too convinced, but i can understand any colleague who would rather record too much today and then downsample, as opposed to finding you won't be able to fully exploit future distribution formats with your legacy material. if i'm not maxing out my equipment in terms of cpu cycles, there is no harm done in erring on the side of caution, if high sample rates don't incur higher costs as they go through the workflow. as a counter-example, a tv production i'm involved in uses 96k initially, but only because the live sound desk is a midas which cannot do less. it is immediately downsampled to 48k before going onto the broadcast network via dante, because nobody wants to put up with the extra data and doubled loadin/transfer times. actually, i just had a behringer ada8000 die on me, and i will probably replace it with some 96khz capable kit from directout. i don't expect to find anything interesting, like you said, but i'm going to try it nonetheless. i know that my tweeters will only begin to roll off at 40khz. i'm not advocating high sample rates, but hey, "because i can" has always been a strong incentive :-D the main problem is that some equipment actually gets worse at high sample rates, and putting a 192k sticker on your box is actually more important than getting 48k really right... -- Jörn Nettingsmeier Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487 Meister für Veranstaltungstechnik (Bühne/Studio) Tonmeister VDT http://stackingdwarves.net