28 Bedrock SMxx operating manual © Bedrock Audio BV, 2019
7. Level and spectrum
7.1 SPL meter
The Bedrock SMxx, as a Sound Pressure Level meter (also known as SPL meter or SLM)
complies either with IEC 61672 Class 2 and ANSI S1.4 Type 2 (SM30 and SM50) or IEC
61672 Class 2 and ANSI S1.4 Type 1 (SM90). It is classified as a group X instrument.
The SPL meter modules features three screens: SPL measurements, settings and browse
measurements.
SPL measurements screen, during measurement (left) and with settings keyboard showing
(right)
The following sound pressure level measurement settings are supported:
• Time weighting: Fast (F) and Slow (S)
• Frequency weighting: Z (linear, unweighted), A-weighted, C-weighted
• Max hold (holds and displays the maximum level during the measurement
interval; used with either Fast or Slow time weighting)
• Equivalent continuous (EQ): computes the time-integrated level over the
measurement interval; the level shown corresponds to the level of a contin-
uous signal containing the same amount of energy as the measured signal.
• Peak values (PK): the highest instantaneous value within an interval
Note that MAX and PK are not the same; MAX represents the highest measurement over
a short time averaging period (either FAST or SLOW), and PK represents the highest
instantaneous value in the signal (even if this is a peak of very short duration). The SMxx
allows PK measurements in combination with any frequency weighting, but only LCPK
is commonly used.
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