Normal variation in the masking effectiveness of the narrow band noises of one audiometer

The minimum effective masking levels (MEMLs) of the narrow band masking noises (audiometric frequencies 0.25-4 kHz) of one audiometer were determined for a sample of 40 normal individuals. The variation in MEML was rather wide but it decreased with increasing frequency. After consideration of the plateau procedure for masking, it is recommended that the starting level of masking should be: Threshold of masking+mean MEML+10 dB. This should be sufficient to prevent finding false plateaux and hence obviate the possibility of obtaining a threshold for the test ear which in fact relates to the non-test ear.