tape noise

February 17, 2010
in Category: Process or Progress?, The tapes
0 4282 0

hiss and burn, white black pink noise. Tape hiss is the high frequency noise present on analogue magnetic tape recordings caused by the size of the magnetic particles used to make the tape. Effectively it is the noise floor of the recording medium. It can be reduced by the use of finer magnetic particles or by increasing the amount of tape used per second to record a signal. The small amount of noise present in magnetic recordings can be thought of as arising from two separate and distinct causes –

1) Minute magnetic irregularities in the
tape which vary the amplitude of the
recorded signal.

2) Variations in the speed of the medium
which frequency modulate the recorded signal.

The first of these is a well-known phenomenon and is mentioned here only because it is often
blamed for the second type of noise, which is the subject of this discussion.

Variations in the speed of the magnetic tape can produce a variety of effects in the recorded
program, ranging from wow (long term variations) and flutter (medium long term variations) to
noise, which is the result of very short term speed variations.

In order to be manifested as noise, the rate at which the tape speed is changing must be very much
faster than that associated with the capstan or other parts of the drive system. It has been
found that the principal sources of frequency modulation noise are the varying frictional
forces acting upon the tape as it passes over the recording heads and guides. This action is similar
to that of drawing a bow across a violin string, except that the tape – being highly damped, does
not respond with the “tone” but only the “scratch.”

Noise of this sort may be introduced into the program during either recording or reproducing, although
in most machines the recording function is considerably more susceptible to this effect. A number of noise reduction techniques can be used to reduce the impact of tape hiss, including Dolby NR and DBX.


Cassette concepts connoisseur

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