We shall see later that tension is one of the quantities that determines the pitch of these instruments. It is defined as the ratio of the mass of a body to its volume. The frequency of vibrating strings depends on the mass of the string divided by its length. In discussing the propagation of sound waves in air we shall see that the velocity depends on the air pressure. We define energy or work in joules as the product of a force in newtons and the distance through which it moves d in meters.
Power is the rate at which work is done or the rate at which energy is being used up or radiated.
The characteristics of sound waves, such as speed, frequency, and wave length and their properties reflection, refraction, and diffraction, are discussed in Chapter 3. These quantities are used in later chapters describing stringed, wind, and percussion instruments and in architectural acoustics. In Chapter 4 the anatomy of the ear is discussed as is the relationship between the musical terms pitch, loudness, and timbre and their physical counterparts. In Chapter 5 we shall look at what makes our present musical scale unique, explaining why this is the only acceptable scale for Western music. Chapter 10 is devoted to an analysis of architectural acoustics.