Experimenting with sound in vacuum

Even though my vacuum chamber is quite basic, now that I have it there is no shortage of ideas to do with it. I once heard the saying that "nobody can hear you scream in space". So I decided to to see if it was true.

First I learnt that sound consists of waves of air pressure. That explains why you can't hear sounds in space, because there is no air.

Sound waves are longitudinal which means that air particles oscillate forwards and backwards much like a slinky. This is very different to other waves like light where they oscillate sideways like when you shake a string.

I also learnt about amplitude and frequency. Amplitude is what defines the how loud the sound is. Whereas frequency determines the pitch, the higher the frequency the higher the pitch is.

During my research I learnt about other things like the Doppler effect and how speakers work. A thing I particularly enjoyed was this video from Animagraffs which is one of my favourite channels in YouTube: https://www.youtube.com/watch?v=RxdFP31QYAg

For the experiment I decided to use a buzzer instead of a wireless speaker for several reasons including because I don't know if it might blow up at such low pressure (which is equivalent to an altitude of 15km). Also, the buzzer is compact and small, specially when powered by a coin cell battery. It looks more resistant and lower cost than my dad's wireless speaker :)

First I put the buzzer with battery into vacuum chamber. Then I closed the chamber and extracted as much air as possible. I also used an app on tablet to measure decibels (which is the unit to measure the loudness of sound). Like in previous experiments I measured the pressure with the pressure sensor and the Micro:bit. The sound was annoying at the beginning but after extracting the air it became bearable. Sadly, I then had to open it. In the video, hopefully you can hear the difference as well.