Cleaning up recordings / recording formats

[fartwell2000]

--- In bellhistorians at y..., "oakcroft13" <bill at h...> wrote:
> In answer to Alan's question: the software package I use for sound 
> editing is Syntrillion's Cool Edit, which I have found very 
powerful. 
> It is shareware, but you can download a trial version and use it 
for 
> 30 days (with restrictions) before you have to purchase it. It is 
> available from www.syntrillion.com. Its most useful facilities are:
> * it can record via the PC soundcard from whatever recorder you use
> * it can record from a directly attached microphone, especially 
> useful for laptops
> * it can translate between all the standard formats, 
especially .wav 
> and .mp3
> * it has extensive capabilties for editing, transformation, 
selective 
> amplification, enveloping, noise removal etc.
> 
> There are other packages too, I'm only recommending this one 
because 
> I use it and it works. If you only wish to digitise recordings, not 
> edit them, Windows Sound Recorder (free!) will work fine, but there 
> are some tricks not covered in the documentation required to make 
it 
> use the file format you want. Also, you may have to download a 
> seperate mp3 codec.
> 
> (I apologise to Macintosh users that I am only covering PC work 
here, 
> perhaps someone who understands Macs better could join in!)
> 
> As regards recording formats, I always record at 44,100 samples per 
> second, 16 bit data, mono. This can lead to very large files 
> (fortunately I have a big hard-drive!). When I add recordings to my 
> database I reformat them as mp3, which gives a reduction in file-
size 
> of over ten times. I also edit out initial silence, trim the 
> recordings to length, etc. I archive the big .wav files off to CD 
in 
> case I ever need them again.
> 
> Here are some thoughts on recording formats.
> 
> Sampling rate: the Nyquist theorem, grossly summarised, says that 
you 
> need to sample at double the maximum frequency present in the 
sound. 
> In practice I find with recordings you need to go higher than that. 
> To sample at 22,050 runs the risk of losing frequencies somewhat 
> below 10 kHz. Therefore, I always use 44,100. Do NOT digitise at 
> 48,000 as some Windows drivers have bugs at this sampling rate.
> 
> Number of bits: 8 bit data gives disappointing results, 32 bit data 
> is complete overkill and is not universally supported. Use 16 bit.
> 
> Number of channels: except for recordings in exceptional 
> circumstances (e.g. recording a swinging bell close up) I do not 
> believe stereo adds any value - save the disc space and use mono.
> 
> File format: .wav files using PCM format are guaranteed to give you 
> back exactly what went in, but at the expense of large amounts of 
> disc (over 5 Mbyte per minute).
> .wav files using the ADPCM format are also guaranteed to give you 
> back almost exactly what went in, and are 25% of the size of PCM 
> format files. In trials I conducted last year, I could detect no 
> difference in the sound of PCM and ADPCM recordings. Disc usage is 
> 1.3 Mbyte / minute.
> .mp3 files are very compressed. The format I use (56k bits/sec on 
the 
> Cool Edit menu) reduces file sizes by a factor of 12. If the 
original 
> recording is high quality then this mp3 format gives moderately 
good 
> reproduction. However, if the original recording is distorted (i.e. 
> the bells were too loud for microphone or recorder), or there is a 
> big wash of background harmonics, mp3 gives a very poor result. 
Disc 
> usage is about 420 kByte / minute.
> 
> The only exception to the above rules, of course, is if the 
original 
> recording is of such poor quality (e.g. severely bandwidth limited) 
> that digitising at 44,100 is not warranted.
> 
> I've written enough now, more (if people think it is useful) in a 
> follow-up post on recorders, microphones, loudness, distortion, and 
> how to get Windows Sound Recorder to record and save in your chosen 
> file format.
> 
> Bill H

Please continue Bill,it is very interesting.
I am sure that many of us have tried making analogue recordings of 
bells and have at times been dissapointed with the results.
Alan