Sound call the waves of mechanical deformations extending in any rather elastic medium (liquids, solid bodies, gases). As well as other waves, a sound it is characterized, in particular, by the frequency of fluctuations. Depending on entry conditions it is possible to find sound frequency in different ways.
It is required to you
- - calculator;
- - physical reference book;
- - tachometer;
- - sound sensor;
- - oscillograph.
Instruction
1. Find the frequency of sound vibrations if length of their waves and acoustic speed in the environment where they extend is known. Calculations should be made on a formula F=V/L. Here V - acoustic speed in the environment, and L - the wavelength (known size). Values of acoustic speeds for different environments can be learned from physical reference books. So, for air under normal conditions (temperature around 20 °C and pressure close to atmospheric) this value is 341 m/s. Therefore, for example, sound vibrations in air with wavelength in 0.25 m will have the frequency of 341/0.25=1364 Hz.
2. To find the frequency of sound vibrations, knowing their period, it is possible on a simple formula: F=1/T. Pay attention that for obtaining the correct values of frequency presented in hertz, the period of T has to be expressed to the SI system, that is have dimension in seconds.
3. For obtaining frequency of the sound vibrations extending in the real environment conduct a physical experiment. Use the specialized device - the tachometer. Today tachometers, as a rule, have high precision of measurements and display information in finished form on the digital indicator.
4. In the absence of the tachometer for finding of frequency of a sound it is possible to use the microphone or other sound sensor with sufficient sensitivity and also an oscillograph. Connect the sensor to an oscillograph and create conditions for receiving a signal (for example, place the sensor on the studied Wednesday). Pick up sensitivity of an oscillograph so that fluctuations on the screen were displayed with a sufficient amplitude. By frequency trim of development achieve display of the steady picture. Learn the period of sound vibrations, being guided by a device scale. Find frequency, using the method described in the second step.