Sound And Waves Flashcards
What do all the ways to measure the speed of sound involve ?
They all involve measuring how long it takes sound to travel over a measured distance
Explain the method for measuring the speed of sound that involves firing a pistol.
A starting pistol is fired a known distance away from a person with a stopwatch. This person starts the stop watch when they see the puff of smoke and stops the stopwatch when they hear the bang of the pistol because light travels faster than sound. Sometimes a sound operated flash is used, when the pistol sounds it then flashes. It is easily seen from a long distance away.
Explain the hammer technique for measuring the speed of sound.
The hammer striking the plate sends out a sound wave. The sound wave passing the first microphone starts. This can be done electronically, sound wave passes microphone 1 and starts timer then stops timer as it passes microphone 2 .
What are waves?
Waves are a way of transferring energy and so transmitting signals. Some examples of waves are sound waves, light waves, water waves and radio waves.
What is the crest and trough?
Crest is the top of the wave sometimes called peak.
The trough is the bottom of the wave.
What is the wave length?
The distance from a point on a wave to the next similar point e.g. from a crest to the next crest. Symbol lambda measured in meters m
What is the frequency?
Frequency is the number of complete waves occurring each second. Frequency is measured in hertz Hz.
What is the wave speed?
The speed or velocity a wave travels at is measured by the distance it travels in a given time Normally one second. Wave speed is measured in meters per second m/s.
What is the amplitude?
The amplitude of a wave is the distance from the horizontal line through the middle of the wave to the peak of the crest or the bottom of the trough see diagram above.
How do you measure the speed of sound and waves?
Wave speed = distance
Time
V (m/s)= d (m)
t (s)
Wave speed = frequency( Hz) x wavelength(m)
Speed of sound= distance
Time
Explain the morse code telegraph
When the tap key is pressed a circuit is completed and the message is transmitted or sent out.
At the other end of the wires, completing the circuit enables a buzzer to sound. The buzzer is the receiver. A code of long or short buzzes can be sent. The invention of the morse code telegraph meant that message could be sent over long distances in very short time and that the could be private.
Explain the telephone ☎️
In the mouthpiece (transmitter) a microphone changes sound energy into electrical energy. After the electrical signal is transmitted along wires it ends up at the ear piece (receiver) where a loudspeaker changes electrical energy into sound energy.
The electrical signal travels between the two telephones at a speed of almost 3000000 m/s which is many times faster than sound in air 340 m/s.
Explain telephone communication.
The electrical signals travelling between telephones varies with the speech producing it. An oscilloscope can be used to show this effect.
Opposite is the trace seen on an oscilloscope when a person speaks into a microphone connected to the input. The pattern is very jagged because of all the different sounds used to make up each word we say.
If we feel signals from pure sounds into an oscilloscope much patterns are seen loud sound soft sound low frequency sound high frequency sound.
Explain a loud note
The trace has a large amplitude measured from the mid line to a peak.
Explain a soft note
The trace has a small amplitude.
