Music and noise. Chapter VII review

Chapter VII studied sound. A sound source vibrates; frequency ν (Hz); the audible range is 16–20 000 Hz, below it infrasound, above ultrasound. Sound needs a medium and does not travel in a vacuum; its speed in air at 20 °C is 343 m/s (331.5 at 0 °C), in water about 1500 m/s and highest in solids (iron about 5850 m/s). Loudness — amplitude (dB), pitch — frequency, timbre — overtones. Echo: h = v · t : 2; echo sounder, ultrasound scan. Musical sound and noise; absorption coefficient; architectural acoustics. Over the year physics studied the structure of matter, motion and force, pressure, energy, machines, heat, electricity, light and sound; the main method is observation, experiment, measurement and calculation. Apply rules thoughtfully and always follow safety: loud sound, boiling water, electricity and sunlight can be dangerous.