Sound waves are so habitual that people seldom think of their nature, of why in general perception of a sound is possible. Meanwhile, sound waves submit to certain laws – in particular, have such parameter as length. To determine length of a sound wave, it is necessary to carry out rather simple calculations.
It is required to you
- - frequency meter;
Instruction
1. At school the people get acquainted with such concept as sound frequency. The human ear is capable to perceive sound vibrations in the range from 16 to 20000 hertz therefore producers of the sound recording equipment, in particular, are guided by this range. To measure sound frequency in hertz and kilohertzes it is habitual, but what is meant by wavelength?
2. Wavelength is equal to the relation of its speed to frequency. At the same time it is necessary to consider that the speed of distribution of a sound in different environments – air, water, a stone, etc. is not identical. The Wednesday is more dense, the distribution speed is higher. If with a normal pressure and temperature of 15 °C the acoustic speed is equal in air 340 meters per second, then in water it can be up to one and a half kilometers per second. The exact value depends on salinity of water and its temperature.
3. From the ratio given above it is visible that for determination of length of a sound wave it is necessary to know its frequency. For example, the sound wave has the frequency of 200 Hz. To what length does this value correspond? If the sound extends in air, its speed is equal to 340 m/s. Means, for determination of wavelength it is necessary 340 to divide into 200, the result is equal 1.7 meters. And to what frequency there corresponds the wavelength of 10 meters? In this case it is necessary to divide acoustic speed into wavelength, the frequency of 34 hertz turns out. The human ear is still capable to perceive such frequency.
4. In practice the determination of frequency of a sound appears the most difficult task, special devices – frequency meters are for this purpose used. In the simplest case the microphone is connected to the device, readings are taken from a scale. If the sound is recorded with the carrier, use of special computer programs is possible. At last, there is very old way of measurement of frequency by means of a tuning fork. Such tuning fork has a moving crossbeam and a scale, readings are taken at the time of the greatest vibration of mustache of the device. Vibration speaks about emergence of a resonance owing to coincidence of frequencies of a sound wave and a tuning fork.