Bell recordings

oakcroft13 bill at h...
Fri Mar 1 11:55:52 GMT 2002

Stephen Ivin:

> warning against allowing the record level to go above
> 5 or 10 db below the max, because of the brief but
> high intensity upper partials

The advantage of viewing the recording in a sound-file editor is that 
you can see the instantaneous peak amplitude and set the recording 
level appropriately. Experience has shown me that this peak can be 
extremely large, and extremely brief in duration.

> for analysis purposes then it is surely preferable to
> have the microphone in the same space as the bell, say 3
> or 6 ft. away.

I found that at least 10 or 15 feet was necessary with my video-
camera (which did not have a record level control), and even then, 
though there was no audible distortion, the peaks were considerably 
clipped. The problem with clipping and distortion in recordings for 
analysis is that it can introduce false partials (due to harmonics, 
one supposes) which are indistinguishable from the real ones. I have 
a number of recordings which are spoilt because of this.

> I know Bill had some difficulties with his laptop
> recording at Dorking.

Not just Dorking, and not just me!

> plug into the less sensitive 'line' input - or with
> a PC to select line and mute mic if both share a socket.

My laptop doesn't have a line input (without I buy a port extender, 
which probably costs a lot more than a good quality mike!). I am 
hoping to do some trials soon with the OU department of musical 
acoustics to take advantage of their experience and finally define a 
procedure and equipment which gives robust results.

Bill H

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