Intro to Sound

We're gonna start now introducing some aspects of sound, so here's a question for you to consider.

Walsh, Diane 0 minutes 12 seconds

If music is playing in an elevator and no one is a riding the elevator, is there sound?

Walsh, Diane 0 minutes 21 seconds

Does sound need an ear to be perceived and to be heard, so you can think about this in in several different ways and it brings us to really think about some different definitions of sound.

Walsh, Diane 0 minutes 38 seconds

So there is a psychological angle 2 sound.

Walsh, Diane 0 minutes 43 seconds

There's the act of hearing.

Walsh, Diane 0 minutes 45 seconds

It creates an auditory experience.

Walsh, Diane 0 minutes 48 seconds

You walk into a busy store and you're hearing lots of people and product hitting the the shelves.

Walsh, Diane 1 minute

You're having this auditory experience?

Walsh, Diane 1 minute 2 seconds

Maybe someone you're with starts to talk to you, so that's like the psychological aspect that's happening through our perception in the brain.

Walsh, Diane 11 minutes

So inertia once again is the tendency for a mass at rest to remain at rest and a mass in motion to remain in motion.

Walsh, Diane 11 minutes 11 seconds

So really vibration, it involves an interesting balance of elasticity and inertia.

Walsh, Diane 11 minutes 21 seconds

So molecules in vibration, they won't stop moving until that system loses energy.

Walsh, Diane 11 minutes 29 seconds

If there's enough resistance to cause it to stop, so elasticity, will you bring that object back?

Walsh, Diane 11 minutes 39 seconds

Inertia we're thinking of as once that object is in motion, it's going to stay in motion until it reaches a certain amount of resistance.

Walsh, Diane 11 minutes 48 seconds

So let's imagine.

Walsh, Diane 11 minutes 49 seconds

Here's our molecule once again.

Walsh, Diane 11 minutes 51 seconds

It's set into motion, so now it's gonna keep going until a because of inertia.

Walsh, Diane 11 minutes 59 seconds

Once it's in motion, it's gonna keep going in motion.

Walsh, Diane 12 minutes 2 seconds

Then it reaches enough resistance.

Walsh, Diane 12 minutes 5 seconds

It loses some energy behind it that it stops now.

Walsh, Diane 12 minutes 9 seconds

We think of elasticity and elasticity's gonna come into play and bring that molecule back to its starting position.

Walsh, Diane 12 minutes 21 seconds

Well, and then we'll see even more inertia.

Walsh, Diane 12 minutes 24 seconds

That's gonna keep it going past it's original starting point, so by bration involves a balance of elasticity and inertia.

Walsh, Diane 12 minutes 36 seconds

So we'll see this apply to molecules of air for our examples very shortly.

Walsh, Diane 12 minutes 43 seconds

But to start off with more of a physical model to help with this is an image from the barman text.

Walsh, Diane 12 minutes 50 seconds

Let's think of a physical model here that has a ball attached to a a spring.

Walsh, Diane 13 minutes

There you go and attached so the spring has a certain degree of elasticity to it.

Walsh, Diane 13 minutes 5 seconds

This ball is at equilibrium.

Walsh, Diane 13 minutes 7 seconds

It's at its center point now.

Walsh, Diane 13 minutes 9 seconds

Here comes our displacement force that pulls down that spring.

Walsh, Diane 13 minutes 17 seconds

So with some nice Newton's third law kicking in for every action, there is an equal and opposite reaction.

Walsh, Diane 13 minutes 26 seconds

There is an elastic elasticity of this spring that will also help and bring the ball back past its equilibrium, and then the displacement force happens in the opposite direction and then with some restorative forces, that ball comes back to its center resting place.

Walsh, Diane 13 minutes 50 seconds

So once we get to #2 here in this point, we have inertia.

Walsh, Diane 13 minutes 57 seconds

And and the momentum of the ball helping that movement.

Walsh, Diane 14 minutes 4 seconds

So inertia is gonna let it keep going and not opposite direction.

Walsh, Diane 14 minutes 8 seconds

And then it will have some elasticity that brings that ball back to its starting place.

Walsh, Diane 14 minutes 16 seconds

So we have a nice vibration in the motion, so let's apply this now to sound waves.

Walsh, Diane 14 minutes 25 seconds

There's a sound.

Walsh, Diane 14 minutes 27 seconds

Waves are a pressure wave.

Walsh, Diane 14 minutes 30 seconds

That pressure wave could be like another wave.

Walsh, Diane 14 minutes 34 seconds

Whoops to say this is a disturbance.

Walsh, Diane 14 minutes 39 seconds

A disturbance in a medium that is perceptible to the human ear.

Walsh, Diane 14 minutes 49 seconds

If we bring us back to that initial question in the elevator, we do have a little philosophical challenge, but when those pressure changes are perceived by the auditory system, and that signal travels to the brain, we have our idea of sound.

Walsh, Diane 15 minutes 9 seconds

So of course, that's gonna bring in the auditory system.

Walsh, Diane 15 minutes 13 seconds

But in terms of speech production, speech production is the process of producing sound waves.

Walsh, Diane 15 minutes 21 seconds

Part of that process and speech production comes from the larynx of we'll talk much more about that across this course.

Walsh, Diane 15 minutes 30 seconds

So let's review a couple of things.

Walsh, Diane 15 minutes 33 seconds

Sound is a form of energy.

Walsh, Diane 15 minutes 37 seconds

It's not a physical substance.

Walsh, Diane 15 minutes 39 seconds

It has no mass or weight to it.

Walsh, Diane 15 minutes 43 seconds

It's really a disturbance in a medium.

Walsh, Diane 15 minutes 47 seconds

It can be audible when that disturbance reaches.

Walsh, Diane 15 minutes 51 seconds

Say the tympanic membrane and we have the entire process of the auditory system.

Walsh, Diane 15 minutes 58 seconds

Alright, so we're gonna stop here with our introduction to sound.