Audition: Loudness

Language of Loudness: Definitions and Terminology

Although we know what loudness is, we may not be aware of the exact definition and terminology used for loudness. Loudness is the perceptual strength of a sound that ranges from very soft (or quiet) to very loud. Loudness is the primary perceptual correlate of the level of a sound. The study of loudness is a subarea of psychoacoustics. Psychoacoustics is the study of the relationship between physical properties of sound (e.g., frequency, level, and physical duration) and our perceptual response to them (e.g., pitch, loudness, and subjective duration).

Loudness is often erroneously described as the “volume” or “intensity” of a sound. The term volume is used to describe a percept different from loudness and should not be confused with loudness. Volume refers to the subjective size of a sound. The term intensity refers to a physical property of a sound, which is related to its level. A common unit of measure is sound pressure level in decibels, or dB SPL, which is the logarithmic ratio of intensity. Therefore, the terms volume and intensity should not be used interchangeably with loudness.

Since the late 18th century, it has been common for composers to use written notation to indicate the level at which a piece of music should be played to produce a corresponding loudness. These are called dynamic markings and are usually in Italian. Examples of dynamic markings are pianissimo (very soft), mezzo piano (medium soft), forte (loud), and fortissimo (very loud). These dynamic markings refer to relative levels, rather than to specific levels, so that a passage of music may be a little louder or softer than another. Music notation also includes words to indicate a general increase (crescendo) or decrease (decrescendo or diminuendo) in loudness. In addition, a composer can indicate that one note should be louder than the other notes by using accents. Such notations help to give music the proper loudness dynamics and indicate the beat of the music.

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