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20 50 100 200 500 1000 2000 5000 10,00020,000 FREQUENCY (Hz)

20 50 100 200 500 1000 2000 5000 10,00020,000 FREQUENCY (Hz)

FIG. 6.4.2 Weighting curves for sound level meters (after ISO recommendation). The A, B, and C weightings are standards; the D curve is proposed for monitoring jet aircraft noise.

identified as dBA, dBB, dBC, etc; they are called sound level readings to distinguish them from SPL readings which are not modified by frequency.

Many sound level meters have a fourth or flat characteristic which is slightly more uniform than C weighting. It is used in frequency analysis. Still another characteristic, D weighting, is proposed for jet plane noise measurements. Figure 6.4.2 shows the response curves provided by these weighting networks.

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