Hello Mark, On Friday, 20 November 2015 20:22:34 UTC, mako...@yahoo.com wrote:> On Friday, November 20, 2015 at 2:43:24 PM UTC-5, Victor Reijs wrote: > Is the y axis dB below full scale? > If so, those are pretty low levels.It is the dB directly from Audacity's 'Frequency Analysis'. It is indeed a quite low volume (it is silence in a room). All the three plots are of silences in the same room, but different sampling freq. and/or bit depth (and at slightly different times). If I use the line-in without any source connected, I get this FFT Frequency Analysis (using audacity): https://photos.google.com/search/_tra_/photo/AF1QipMW2jfVERXorlDwiakFRuCnxPwx0l-79qqvPwI_ In this case the recording level was 100 (while in the other plots it was around 45).> What kind of recorder is it.Zoom H1: https://www.zoom-na.com/products/field-video-recording/field-recording/zoom-h1-handy-recorder> The noise may be unwanted crosstalk from the digital circuits into the > analog. If they are below the frequency range of your interest, high pass them away.In some way, I might be interested in low frequencies, as neolithic chambers and their passages can behave as Helmholtz resonator (resonance frequency around 10 Hz). So that is why I was thinking in changing the sampling frequency or bit depth for two recordings. In that case I hope the internal recorder noise's peaks will change with the bitdepth and sampling rate, while the real sound peaks stay the same... What do you think?> If the acoustical signals you want to study are very low level, then you may benefit from an external preamp to increase the electrical signal level before it enters your recorder. That will relatively reduce the level of this unwanted noise.That sounds a good idea. In the case I am interested in infrasound, I just use an amplifier that has a low pass filter (say 40 Hz). Thanks for that hint!!! All the best, Victor
low freqeuncy peaks in FFT
Started by ●November 20, 2015
Reply by ●November 21, 20152015-11-21
Reply by ●November 21, 20152015-11-21
On Saturday, 21 November 2015 11:18:20 UTC, Victor Reijs wrote:> If I use the line-in without any source connected, I get this FFT Frequency Analysis (using audacity): > https://photos.google.com/search/_tra_/photo/AF1QipMW2jfVERXorlDwiakFRuCnxPwx0l-79qqvPwI_ > In this case the recording level was 100 (while in the other plots it was around 45).If I use a recording level 100, one sees: https://photos.google.com/search/_tra_/photo/AF1QipOc9xF3qmfjIhftOTSu0LvltzPIMHskcUkyJFV2
Reply by ●November 21, 20152015-11-21
On 11/21/2015 6:21 AM, Victor Reijs wrote:> On Saturday, 21 November 2015 11:18:20 UTC, Victor Reijs wrote: >> If I use the line-in without any source connected, I get this FFT Frequency Analysis (using audacity): >> https://photos.google.com/search/_tra_/photo/AF1QipMW2jfVERXorlDwiakFRuCnxPwx0l-79qqvPwI_ >> In this case the recording level was 100 (while in the other plots it was around 45). > > If I use a recording level 100, one sees: > https://photos.google.com/search/_tra_/photo/AF1QipOc9xF3qmfjIhftOTSu0LvltzPIMHskcUkyJFV2404. That�s an error. The requested URL was not found on this server. That�s all we know. -- Rick
Reply by ●November 22, 20152015-11-22
On Saturday, 21 November 2015 17:42:16 UTC, rickman wrote:> 404. That's an error. > > The requested URL was not found on this server. That's all we know.Don't know why you get this... I see the pictures (but that is perhaps because I am the uploader...) Are you login- into Google photo? Sorry I am not yet used how to properly use these services... Hope someone else knows why you get this 404. All the best, Victor
Reply by ●November 23, 20152015-11-23
On Sunday, November 22, 2015 at 7:22:45 AM UTC-8, Victor Reijs wrote:> On Saturday, 21 November 2015 17:42:16 UTC, rickman wrote: > > 404. That's an error. > > > > The requested URL was not found on this server. That's all we know. > > Don't know why you get this... I see the pictures (but that is perhaps because I am the uploader...) Are you login- into Google photo? Sorry I am not yet used how to properly use these services... Hope someone else knows why you get this 404. > > All the best, > > > VictorI also get 404.
Reply by ●January 21, 20162016-01-21
On Friday, November 20, 2015 at 10:57:16 AM UTC-6, Victor Reijs wrote:> How do I send a picture on this group? > I used in Audacity Effects -> Normalize... -> 'Remove DC offset' before the analusis.A cheapo way: twitter account, tweet a photo, post a link to it. (Alternatively, a G+ account) Like this ... The Outer Limits: Genesis (cover photo) https://twitter.com/Federation2005/status/664241805249015808 ... or this ... Lydia (my female clone/alter ego; the male clone is in the cover photo) https://twitter.com/Federation2005/status/676934002159296513 ... or to have some fun with it ... !!X-RAY VISION!! "The Dark Lord sees all." (*reverse* image layering demo: seeing straight through fog and rain drops) https://twitter.com/Federation2005/status/631230752814837760 "His gaze pierces shadow" (The shadow of the Saint Louis Arch is removed) https://twitter.com/Federation2005/status/631232513571057664 "His gaze pierces Earth" (X-ray right through solid matter to the sky and ground behind it) https://twitter.com/Federation2005/status/631232762276544512 "His gaze pierces flesh (and through to flesh)" (Poor woman never saw it coming) https://twitter.com/Federation2005/status/631234972095877120 Pretty woman. Wish I had X-ray vision. :) Oops. Not like that. https://twitter.com/Federation2005/status/631230265289879552