To gradually diminish or fade away in sound or intensity.

धीरे-धीरे कम होना या खत्म होना।

English Usage: As the speaker concluded, his voice began to trail off.

Hindi Usage: जैसे ही वक्ता ने समाप्त किया, उसकी आवाज धीरे-धीरे कम होने लगी।