Vibrations and Sound Flashcards by Sarah Oliver

What is the frequency of a vibrating object? and its unit of measurement

The number of cycles occurring per second. It’s measured in Hertz (Hz)

How well did you know this?

Not at all

Perfectly

What form does sound travel in?

Wave

How well did you know this?

Not at all

Perfectly

Explain acoustics

The science of designing theatres or concert halls with the correct balance of reflection and absorption of sound

How well did you know this?

Not at all

Perfectly

What is reflection of sound

echo

How well did you know this?

Not at all

Perfectly

How do we know sound waves undergo refraction

Sounds are heard clearer over water or on a cold

How well did you know this?

Not at all

Perfectly

How do we know sound waves undergo diffraction

Can hear around corners

How well did you know this?

Not at all

Perfectly

What is the relationship between the frequency and the vibrating source producing it

The frequency of sound is the same as that of vibrating source producing it.

How well did you know this?

Not at all

Perfectly

What is the amplitude

The maximum displacement of any molecule from it’s rest position

How well did you know this?

Not at all

Perfectly

What type of wave is sound

It needs a medium to travel through. It is a longitudinal wave- the molecules vibrate parallel to the direction in which the compressions and rarefactions travel.

How well did you know this?

Not at all

Perfectly

What is the speed of sound in air

331m/s

How well did you know this?

Not at all

Perfectly

What s the relationship medium density and the speed of sound in that medium

The denser the medium the greater the speed

How well did you know this?

Not at all

Perfectly

What is an overtone

Frequencies are multiples of certain frequency
ex: f is a given frequency
2f is the first overtone
3f is the second overtone

How well did you know this?

Not at all

Perfectly

What is loudness of a sound wave what depend on

It depends on the amplitude and frequency of a wave, The greater the amplitude the greater the loudness

How well did you know this?

Not at all

Perfectly

What is pitch and what does it depend on

It depends on the frequency of the wave. The higher frequency the higher the pitch. The lower the frequency the lower the pitch

How well did you know this?

Not at all

Perfectly

What is the quality of a note and what does it depend on

It depends on the number of overtones present in the note and the relative strengths of the different overtones present

How well did you know this?

Not at all

Perfectly

What are the frequency limits of audibility

Highest and lowest frequencies that can be heard by a normal human ear. Range is 20 Hz- 20,000 Hz

How well did you know this?

Not at all

Perfectly

What are frequencies above 20,000 Hz called

ultrasonic

How well did you know this?

Not at all

Perfectly

What is the natural frequency

Any object free to vibrate will do so at a certain frequencies the predominate of which is it’s natural frequency of vibration

How well did you know this?

Not at all

Perfectly

Explain resonance

If frequency of a periodic force is the same as it’s natural frequency the body will vibrate at a large amplitude. This phenomenon is resonance

How well did you know this?

Not at all

Perfectly

Give four examples of resonance

Barton’s pendulum
Wire on a sonometer with a tuning fork
Buildings in an earthquake
Shatter glass, natural frequencies is the same as some high notes

What is the threshold of hearing

The smallest sound intensity detectable by the average human ear at frequency of 1kHz

What is sound intensity

It is the rate at a point which sound energy is passing through unit area at rights angles to the direction in which the sound is travelling at that point

What is the unit of sound energy

Watt per square metre Wm^-2

What is sound intensity level measured in

decibels (dB)

What frequencies is the ear most sensitive between

2000Hz and 4000Hz

When sound intensity in Wm^-2 is doubled what happens to the sound intensity level?

Increases by 3dB

What is a sound level meter used for

It uses a dBA (Decibel adapted) scale, to take account of the vibration in the human ears response to sounds of different frequencies

What damage can noise do and why noise protection needed

Partial deafness due to being exposed to loud sounds is incurable.Industry workers/farmers war ear protection when working with loud machinery

Explain a string vibrating at it's fundamental frequency

A string vibrating with an antinode at it's centre and a node at either end (with no others) is vibrating at it's fundamental frequency

What is the relationship between the length of string and its fundamental frequency

Greater the length the lower the fundamental frequency. Fundamental frequency of a string is inversely proportional to it's length. f is proportional to 1/l

How can F is proportional to 1/l be verified

With a sonometer - to investigate the variation of the fundamental frequency of a stretched string

Explain harmonics

Frequencies which are multiples of a certain frequency F are harmonics. F is 1st harmonic and the fundamental frequency. 2f is the second harmonic etc...

What is the formula for the fundamental frequency of a string

f= 1/2l (square root of T/mass per unit length)

How is fundamental frequency proportional to Tension

f is proportional to the square root of T

How is fundamental frequency proportional to mass per unit length

f is proportional to 1/square root of mass per unit length

Explain how stationary waves act in a pipe closed at one end

There is a node at the base of the pipe.- molecules do not vibrate The amplitude increases as you move up and there is an antinode at the top of the pipe- molecules vibrating with a max amplitude.

How does resonance occur in a pipe

If pipe's length is varied resonance will occur at certain lengths

Explain how stationary waves act in a pipe open at both ends with an example

There must be an antinode at each end. In open pipe all harmonics may be present. Tin whistle is an example of a musical instrument which a column of air resonates in a pipe open at both ends

In the experiment variation of the fundamental frequency of a stretched string with it's tension how is the fundamental frequency determined

Changing tuning fork and adjusting tension until resonance is observed

How would the measurements taken In the experiment variation of the fundamental frequency of a stretched string with it's tension be shown on a graph

graph of f against graph of square root T as they are proportional

How does the graph of frequency proportional to tension verify that relationship In the experiment variation of the fundamental frequency of a stretched string with it's tension

there is a straight line through the origin

How would the measurements taken In the experiment variation of the fundamental frequency of a stretched string with it's length be shown on a graph

plot f compared to 1/l

What is the relationship between fundamental frequency and length as shown in the experiment variation of the fundamental frequency of a stretched string with it's tension be shown on a graph

f is proportional to 1/l

In the experiment variation of the fundamental frequency of a stretched string with it's tension how was tension measured

Newton balance

In the experiment to measure the speed of sound in air how was the column of air adjusted, how was the frequency measured and how was the diameter measured

-Open pipe was raised for length Read the frequency from the tuning fork Diameter was measured using a vernier calipers

In the experiment to measure the speed of sound in air how was it known the air column was vibrating at it's first harmonic

The first time resonance - a loud sound is observed

In the experiment to measure the speed of sound in air why do you need to measure diameter of the top of the tube

the wave partially exists above top of tube

How would you find the speed in air doing the experiment to measure the speed of sound in air but not measuring the diameter

You would find the distance between two points of resonance and double this to find the wavelength. multiply wavelength by frequency to get speed