The Learning Circuit 85: How Do Ultrasonic Distance Sensors Work?

Good presentation Karen.

One nit, I would not use c to represent the speed of sound.

c is universally used to represent the speed of light, so using it for sound could confuse some people.

DAB

The speed of sound in mathematical notation is conventionally represented by c, from the Latin celeritas meaning "velocity".

https://en.wikipedia.org/wiki/Speed_of_sound

It is not a universally known notation as I never encountered it during my work career.

The speed of sound was usually given as a mach number with altitude.

c was always the speed of light.

So I do not know where wikipedia came up with that notation, but it was not part of my physics or engineering use.

DAB

"...So I do not know where wikipedia came up with that notation..."

Oxford Dictionary of Physics perhaps ?

https://www.oxfordreference.com/view/10.1093/acref/9780198821472.001.0001/acref-9780198821472-e-2875

"Symbol c or c_s. The speed at which sound waves are propagated through a material medium."

I'm just going to jump in on this as well: In my experience, c is pretty common in aeronautical engineering and pilot-level aerodynamics as notation for the speed of sound at a given altitude. Even Mach numbers are defined as M = u/c where u is airspeed and c is the speed of sound at that density altitude.

I checked my physics books and c is always speed of light.

When I looked up speed of sound they used v or Vs.

So my US text book did not follow the Oxford definition, probably like me, they found it too confusing with the speed of light.

FYI, when I did a project with the Noise and Sonic Boom Information Technology office in the US Air Force, I never saw the speed of sound referred to as c.

DAB

There aren't that many latin + greek letters to have a single letter for each constant or variable, so of course you have to "recycle" them. The lowercase c is also commonly used for specific heat for instance.

There aren't that many latin + greek letters to have a single letter for each constant or variable, so of course you have to "recycle" them. The lowercase c is also commonly used for specific heat for instance.