A police siren emits a sinusoidal wave with frequency fs= 500 Hz. On this cool day, the speed of sound is 340 m/s. What frequency will a stationary listener hear when the police car is moving away at 30.0 m/s? SET UP (Eigure 1) shows our diagram. We use ft. - fs(v +UL)/(v +vs) with ty, = 0 and vg = 30.0 m/s. SOLVE From the equation above. 340 m/s +0 fL = + fs= 340 m/s + 30.0 m/s REFLECT As the siren recedes, the listener hears sound of lower frequency than when the siren is at rest. Part A - Practice Problem: What frequency does the police officer hear? Express your answer with the appropriate units. HÅ 1 Value Submit Request Answer Units ? (500 H₂) = 459 Hx
Properties of sound
A sound wave is a mechanical wave (or mechanical vibration) that transit through media such as gas (air), liquid (water), and solid (wood).
Quality Of Sound
A sound or a sound wave is defined as the energy produced due to the vibrations of particles in a medium. When any medium produces a disturbance or vibrations, it causes a movement in the air particles which produces sound waves. Molecules in the air vibrate about a certain average position and create compressions and rarefactions. This is called pitch which is defined as the frequency of sound. The frequency is defined as the number of oscillations in pressure per second.
Categories of Sound Wave
People perceive sound in different ways, like a medico student takes sound as vibration produced by objects reaching the human eardrum. A physicist perceives sound as vibration produced by an object, which produces disturbances in nearby air molecules that travel further. Both of them describe it as vibration generated by an object, the difference is one talks about how it is received and other deals with how it travels and propagates across various mediums.
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