Diaphone

3-2-115

equipment producing a characteristic sound using a reciprocating piston with vents operated by compressed air. Output can be in the form of two tones at different sound levels, the second tone being at a lower frequency. If there is only one tone, it ends in a suddenly lowered pitch known as a “grunt”.

Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)