When in the 50's
of the last century the "High Fidelity" apparatuses appeared
successfully, the difficulty arose of comparing apparatus of the same functions
but of different manufacturers. Each one specified what he thought fit and in the
way that best suited it. To put order to this chaos were elaborated norms on
the diverse parameters to measure in the reproducers of sound of high fidelity.
Some are only measurement standards, they only indicate how it should be done and
how to express it so that measurements from different manufacturers can be
compared. As an example we have the case of the american norm of measurement
IHF (Institute High Fidelity).
Others are
quality norms, they specify minimum
requirements so that the device can enter the name of high fidelity. The most
widely used of these norms was the one written in 1962-63 in West Germany and
the German Institute for Standardization (DIN). These standards carry the
number 45500 destined to become famous.
Another norm,
often used by the Japanese is the JIS that gives in general better values
than the DIN, so when comparing values of different devices we must ensure
that the norms in which the measurement has been made.
A concept used in
the measurements and that should be clarified is that of the weighting
specified for some measurements. To weigh in this case is to measure a
parameter taking into account the sound sensation produced in the brain each of
the audible frequencies. For example, it is not the same to have a certain
level of noise on a turntable at 400 Hz frequency than at the frequency of 50
Hz. The second creates a noticeably smaller sensation in the brain.
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