**What is a Sound Wave?**

Watch the video below

From previous lectures, we know that amplitude corresponds to the maximum displacement of the wave from the equilibrium position

Amplitude affects the size of the vibrations of the particles in the medium

According to the Phet simulation, as amplitude increases, the sound becomes louder and as the amplitude decreases, the sound becomes quieter

How does Frequency Affect Sound Wave Speed?

Watch the video below

**Sound Waves**

Physics 101

Physics 101

How does Frequency Affect Sound?

How does Frequency Affect Sound?

How does Amplitude Affect Sound?

How does Amplitude Affect Sound?

therefore, frequency does not affect wave speed

At 506 Hz:

Speed=236 m/s

At 1000 Hz:

Speed=236 m/s

How does Amplitude Affect Sound Wave Speed?

At high amplitude

Speed = 236m/s

At low amplitude:

Speed = 236m/s

therefore, amplitude does not affect wave speed

What does Affect the Speed of Sound?

Sound wave speed depends on the properties of the medium which the wave travels through

The speed of a sound wave generally increases moving from gases to solids

The formula for calculating sound wave speed is:

B= bulk modulus (elastic properties of the medium)

p=density

Example

What is the speed of a sound wave traveling through water (20°C) where the bulk modulus of water is 2.2x10^9 N/m^2 and the density of water is 1000 kg/m^3?

Solution

In this question, we are given all the variables needed for finding the speed of the sound wave. Therefore, we can plug in the numbers into the equation below.

If we were not given all the variables, we need to solve for the unknown variables first. For example, if we were not given information about the bulk modulus but given the change in pressure Δp and the fractional change in volume ΔV/V, we can solve for B first using the equation below. After, we can plug the numbers back into the equation for speed (the one used on the previous slide).

Note that the negative sign in front is present in the equation since the sign of Δp is always different than the sign of ΔV/V.

Works Cited

Phet simulation

"Sound." PhET. University of Colorado, n.d. Web. 19 Feb. 2015. <http://phet.colorado.edu/en/simulation/sound>.

Physics 101 Textbook

Hawkes, Robert, Javed Iqbal, Firas Mansour, Marina Milner-Bolotin, and Peter Williams. Physics for Scientists and Engineers: An Interactive Approach. Vol. 1. Toronto: Nelson Education, 2014. Print.

Graphs

http://4.bp.blogspot.com/_hwnCNuE0Gqk/TUs5Dk4iQWI/AAAAAAAAAJ4/E2cKMSlh6kQ/s1600/sound.png

Other

"Pitch and Frequency." Pitch and Frequency. The Physics Classroom, n.d. Web. 11 Feb. 2015. <http://www.physicsclassroom.com/class/sound/Lesson-2/Pitch-and-Frequency>.

a sound wave is a longitudinal wave

it can move in three dimensions

a sound wave passes through a specific medium

the particles of the medium oscillate and create areas of low and high pressure

The particles of the medium in which the sound wave passes move back and forth at a certain frequency

The frequency of a wave is referred to as how often the particles in the medium vibrate as the wave passes through

Frequency is usually measured in Hertz

Frequency affects the speed of the vibrations of the particles

From the Phet simulation, it can be concluded that high frequencies correspond to high pitches and low frequencies correspond to low pitches

Speed = distance / time

Speed = distance / time