I've got several large metal and plastic sheets and they make a peculiar sound when I hold them up from one end and shake them.
The sound can be described as "warbling or wowbling" effect. I've heard the same sound from a wood saw by flexing it. My interpretation is that the sheets are are slightly concave (rather than simply flat) and flexing them applies stresses that are suddenly released and that generates an acoustical shock wave.
The process may be like the snap that's heard from the clicker in a computer mouse, except the frequency is much lower in sheets.
The sound can be described as "warbling or wowbling" effect. I've heard the same sound from a wood saw by flexing it. My interpretation is that the sheets are are slightly concave (rather than simply flat) and flexing them applies stresses that are suddenly released and that generates an acoustical shock wave.
The process may be like the snap that's heard from the clicker in a computer mouse, except the frequency is much lower in sheets.