Flashcards
Sound Waves
Cards in this deck (4)
- 1—
- 2Detecting sound We can detect sound using our ears. An ear has an eardrum inside, connected to three small bones. The vibrations in the air make the eardrum vibrate, and these vibrations are passed through the three small bones (called ossicles) to a spiral structure called the cochlea. Signals are passed from the cochlea to the brain through the auditory nerve, and our brain interprets these signals as sound.Speed of sound
Although sound travels quite fast, it is still possible to measure its speed in air. To do this, you need to measure the time it takes a sound to travel a measured distance. To reduce errors, particularly timing errors, you should either:
use a large distance (preferably over 50 metres), or
use an electronic timer or data logger to record the time taken
Clap-echo method
This method involves measuring the time taken for you to hear an echo from a sharp clap. You stand a long distance from a wall, clap, and listen for the echo. The distance travelled is twice the distance from you to the wall (because the sound has to travel to the wall and back).
One way to reduce timing errors in this method is to clap in time to the echoes. This means that the time between each clap is the journey time for the sound. You then measure the time for 11 claps, which is the time for 10 journeys by the sound. This time can then be used to calculate an average time for the sound to travel to the wall and back.
Using microphones and data logger - 3Ultrasound The frequency of sound waves is measured in hertz, which has the symbol Hz. The bigger the number, the greater the frequency and the higher the pitch of the sound. Human beings can generally hear sounds as low as 20 Hz and as high as 20,000 Hz (20 kHz).High pitched Sound with a frequency of more than 20,000 Hz is called ultrasound. It is too high pitched for humans to hear, but other animals (such as dogs, cats and bats) can hear ultrasound. Ultrasound has many applications in medicine, including ultrasound scans to check on the health of unborn babies.Sound and ultrasound are pressure waves that transfer energy from place to place. Ultrasound can be used to clean jewellery. The jewellery is placed in an ultrasonic bath, where the rapid vibrations shake the dirt loose. Ultrasound can also be used for physiotherapy. Its energy is absorbed by soft tissue in the body, bringing relief from sprains and arthritis (painful joints).
- 4Properties of sound waves When an object or substance vibrates, it produces sound. These sound waves can only travel through a solid, liquid or gas. They cannot travel through empty space. Longitudinal waves Sound waves are longitudinal waves - the vibrations are in the same direction as the direction of travel.Sound waves are produced by all vibrating objects. Loudspeakers work by converting electrical energy into kinetic energy. This moves the cone which creates the sound waves.
Reflection
Sound waves can reflect off surfaces. We hear sound reflections as echoes. Hard, smooth surfaces are particularly good at reflecting sound. This is why empty rooms produce lots of echoes.
Soft, rough surfaces are good at absorbing sound. This is why rooms with carpets and curtains do not usually produce lots of echoes.
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- Citizenship Test physics Flashcards on Sound Waves, created by Archie Aldiss on 06/06/2017.
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- Archie Aldiss
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