This weeks ‘mystery object’ of the week plays around with volume. If you think you know what it is we’d love to hear from you.
Clue …………….prior to the development of electrical amplification this machine was the most effective attempt in increasing the sound volume!
Sound Of The Hound 
Presumably Parsons’s compressed air thing….
Good answer…
It it an amplifier using a carbon microphone whose diaphragm driven electromechanically by the incoming signal to be amplified? And who says thermonic valves gave us the first amplifying device?
Interesting……..
Is it an Auxetophone compressor?
Your bang on target