Sound-Level Meter and Analyzer 



The sound-level meter, General Radio Type 1558-AP 

 Octave Band Noise Analyzer, is a portable, battery-operated 

 audio -frequency spectrum analyzer. The analyzer contains 

 a high-impedance microphone preamplifier, selectable one- 

 octave bandwidth filters, an output amplifier, and an indicat- 

 ing meter. The gain of the analyzer can be set (depending on 

 the sensitivity of the receiving transducer) so that the meter 

 directly indicates the sound pressure level in any of its 

 bands. The frequency response of the analyzer is flat ±1 dB 

 from about 20 Hz to 15, 000 Hz in the ALL PASS position. 

 The output of the analyzer is normally used in the ALL PASS 

 position to provide an input signal to the tape recorder. 

 Table 2 lists the lower and upper cutoff frequencies at the 

 3-dB down points and center frequency for all the octave 

 bands of the analyzer. 



TABLE 2. LOWER AND UPPER CUTOFF FREQUENCIES 

 AND MIDBAND FREQUENCIES FOR THE ONE- 

 OCTAVE BANDS OF SOUND LEVEL METER 



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