Sound waves can propagate through solids, liquids, and gases. In solids, sound waves travel as vibrations of the particles in the medium. In liquids, sound waves travel as pressure waves. In gases, sound waves travel as density waves.

The speed of sound in air at room temperature (20°C) is approximately 343 meters per second.

The relationship between the frequency ($f$), wavelength ($\lambda$), and speed ($v$) of a sound wave is given by the equation $f = \frac{v}{\lambda}$.

The unit of measurement for the frequency of a sound wave is Hertz (Hz), which represents the number of oscillations or cycles per second.

The unit of measurement for the amplitude of a sound wave is Watts per square meter (W/m^2), which represents the amount of power carried by the wave per unit area.

The relationship between the amplitude of a sound wave and its loudness is logarithmic. This means that a small increase in amplitude can result in a noticeable increase in loudness.

The unit of measurement for the loudness of a sound wave is Decibels (dB), which is a logarithmic unit that represents the ratio of the sound pressure to a reference pressure.

The threshold of hearing for humans is approximately 0 dB, which is the point at which sound becomes audible.

The threshold of pain for humans is approximately 120 dB, which is the point at which sound becomes painful.

The phenomenon of sound waves bending around obstacles is called diffraction.

The phenomenon of sound waves bouncing off surfaces is called reflection.

The phenomenon of sound waves changing direction when passing from one medium to another is called refraction.

The phenomenon of two or more sound waves combining to produce a new wave is called interference.

The device used to convert sound waves into electrical signals is called a microphone.

The device used to convert electrical signals into sound waves is called a speaker.