Loudness and Loudness Level

As discussed in Section 4.3.2 which contains an in‐depth description of the loudness of sound, the human ear does not have a uniform sensitivity to sound as its frequency is varied. Figure 4.6 in Chapter 4 shows equal loudness level contours. These contours connect together pure‐tone sounds that appear equally loud to the average listener. Recently, slightly modified contours have been proposed by Moore and coworkers [1–3] (see Figure 6.1). In 2007, a new American National Standards Institute (ANSI) standard (ANSI S3.4–2007) [4] for the calculation of the loudness of steady sounds was published. This 2007 ANSI standard is based on the loudness model of Moore et al. [1]. The model in ANSI S3.4–2007 gives reasonably accurate predictions of a wide range of data on loudness perception [1]. However, the equal loudness contours predicted by the model shown as the dotted lines in Figure 6.1 differ substantially from those in the International Organization for Standardization (ISO) standard that was applicable in the past [5], which in turn were based on the 1956 data of Robinson and Dadson [6]. Similar contours have been determined experimentally for bands of noise instead of pure tones (see Chapter 4).