Sound and Wave Effects
In this topic we relate changes in the shape of an oscilloscope trace to changes in pitch and volume
and relate the impact of different types of waves on living cells to their frequency and the energy carried by the wave.
By the end of this topic you should know:
Sound consists of vibrations which travel as a longitudinal wave through substances.
The denser the medium, the faster sound travels.
The greater the amplitude of the waveform, the louder the sound.
The greater the frequency (and therefore the shorter the wavelength), the higher the pitch.
Sound does not travel through a vacuum.
The speed of sound in air is 330 m/s, a million times slower than light.
When a wave travels through a substance, particles move to and fro.
Energy is transferred in the direction of movement of the wave.
Waves of higher amplitude or higher frequency transfer more energy.
By the end of this topic you should be able to:
Explain observations where sound is reflected, transmitted or absorbed by different media.
Explain observations of how sound travels using the idea of a longitudinal wave.
Describe the amplitude and frequency of a wave from a diagram or oscilloscope picture.
Use drawings of waves to describe how sound waves change with volume or pitch.
Suggest the effects of particular ear problems on a person's hearing.
Evaluate the data behind a claim for a sound creation or blocking device, using the properties of sound waves.
Use diagrams to compare the waveforms a musical instrument makes when playing different pitches or volumes.
Explain differences in the damage done to living cells by light and other waves, in terms of their frequency.
Explain how audio equipment converts sound into a changing pattern of electric current.
Suggest reasons why sound waves can agitate a liquid for cleaning objects, or massage muscles for physiotherapy.
Evaluate electricity production by wave energy using data for different locations and weather conditions.
By the end of this topic you should understand these key words:
Vibration: A back and forth motion that repeats.
Longitudinal wave: Where the direction of vibration is the same as that of the wave.
Volume: How loud or quiet a sound is, in decibels (dB).
Pitch: How low or high a sound is. A low (high) pitch sound has a low (high) frequency.
Amplitude: The maximum amount of vibration, measured from the middle position of the wave, in metres.
Wavelength: Distance between two corresponding points on a wave, in metres.
Frequency: The number of waves produced in one second, in hertz.
Vacuum: A space with no particles of matter in it.
Oscilloscope: Device able to view patterns of sound waves that have been turned into electrical signals.
Absorption: When energy is transferred from sound to a material.
Auditory range: The lowest and highest frequencies that a type of animal can hear.
Echo: Reflection of sound waves from a surface back to the listener.
Ultrasound: Sound waves with frequencies higher than the human auditory range.
Ultraviolet (UV): Waves with frequencies higher than light, which human eyes cannot detect.
Microphone: Turns the pressure wave of sound hitting it into an electrical signal.
Loudspeaker: Turns an electrical signal into a pressure wave of sound.
Pressure wave: An example is sound, which has repeating patterns of high-pressure and low-pressure regions.