Many people now enjoy marine sports such as skin diving and scuba diving in sallow water area. Acoustic signals through an underwater loudspeaker can be used as a simple and effective way of preventing diving accident. At this time, it is fundamentally important to research in advance the masking of objective signals by ambient noises. In our research, measurements of masking effects of auditory ambient noise provide data from which the excitation pattern of the masking stimulus is derived in air and under water, using a pure tone masker and a band-limited noise masker centered at 1200 Hz and 2500 Hz. The present study casts further light on underwater masking results by comparing masking effects in air. The underwater results of masking measured are almost the same as the results in air. Therefore, it can be considered that under water masking effects are obtained on referring to usual experimental masking results in air.
