Topic 50

Question 1

What is sound?

Answer 1

Mechanical vibration transmitted by a medium

Question 2

What is propagation?

Answer 2

In fluid and gases only, longitudinal waves are possible. In solids, transverse waves are possible.

Electromagnetic waves are transverse.

Question 3

Formula proving waves are like a sinus function.

Answer 3

y = y₀ cos[2π((x/λ)-(t/T))]

• y = the displacement of an element or change of the gass*
• t/T = f = Frequency (Height of sound)*

Question 4

Formula to calcualte the speed of propagation

Answer 4

v = λ*f = λT

Question 5

Which factors does the speed of sound depend on?

Answer 5

The medium

The strength of the forces among molecules

Question 6

Speed of sound in water and air

Answer 6

Water: 1500 m/s

Air: 344 m/s

Question 7

What is the frequency range of audible sound?

Answer 7

16Hz - 20000Hz

Question 8

Values of Ultrasound and Infrasound

Answer 8

Ultrasound: > 20000 Hz

Infrasound: <16 Hz

Question 9

What determines the strength of a sound?

Answer 9

Its intensity, power per unit area (W/m²)

Not to be confused with loudness

Question 10

What are the two auditory thresholds?

Answer 10

Lowest audible intesnity = 10^-12W/m²

Pain Sensation = 10 W/m²

Question 11

What is loudness measured in?

Answer 11

Decibels (A logarithmic scale)

Question 12

How are decibels calculated?

Answer 12

10 log (I/I₀)

I = Intensity

Question 13

Name 2 psychophysical laws

Answer 13

Weber-Fechner law

Stevens Law

Question 14

What is the Weber-Fechner Law?

Answer 14

The intensity of sensation is proportional to the logarism of the relative intensity of the stimulus, idependent of the type of receptor.

Question 15

What is Steven’s law?

Answer 15

The intensity of sensation is proportional to the power of the relative intensity of the stimulus

Question 16

What is the doppler effect?

Answer 16

The observed sound depends on if the source or observer are in motion and which direction they are moving.