The ACME Thunderer is what is known as a pea whistle – the body of the whistle contains a ‘pea’ that moves with the airflow to produce its signature rolling trill. It is easy to blow, small, high pitch 117dBA and loud.

The addition of the pea makes it possible to vary the sound produced by the whistle so it is an extremely versatile tool of communication, making it a favourite amongst dog trainers.