Audio Engineering

82 Chapter 3 Research in recent years has advanced the knowledge of atmospheric absorption signifi cantly from the original base ...

Acoustic Environment 83 10 ^6 10 ^5 10 ^4 10 ^3 10 ^2 10 ^1 100 101 102 Absorpt ion coeff ici ent (dB/m) 101 102 103 104 1 ...

84 Chapter 3 3.3 Atmospheric Absorption ........................................................................................ ...

Acoustic Environment 85 the sum of inverse-square-law level change and excess attenuation. Figure 3.3 shows the excess attenuati ...

86 Chapter 3 the frequency interval between comb fi lters from two sources and then converting from frequency to time and fi nal ...

Acoustic Environment 87 Having made the metric conversions and obtained the density fi gure, we can then use the basic equation ...

88 Chapter 3 3.5 Temperature-Dependent Velocity ............................................................................ The ...

Acoustic Environment 89 It can be seen that the velocity is dependent only on the type of gas and the temperature and is indepen ...

90 Chapter 3 Suppose we had “ tuned ” to the peak of a 1000-Hz standing wave in a room fi rst at 72.5°F and then later at 92.5°F ...

Acoustic Environment 91 As the sound source passes the listener and recedes, the pitch swings from 1084 Hz to F    1130 0 11 ...

92 Chapter 3 hear it said, “ The wind blew the sound away. ” That is not so; it refracted away. Even a 50- mph wind (and that’s ...

Acoustic Environment 93 WhereS 1 is absorptive then the equation becomes: Reflected signals relative level  In the case of subs ...

94 Chapter 3 Change in media hence change in velocity Reflected sound Transm itted sound Reflectedsound (1 – a) Flank ing path A ...

Acoustic Environment 95 Example An anechoic room absorbs 99% of the energy received from the sound source. What percentage of th ...

96 Chapter 3 Box 3.1 (Continued) The Sound Pressure Level (in decibels of a sound)—20 times the logarithm to the base 10 of the ...

Acoustic Environment 97 3.12 Classifying Sound Fields .......................................................................... ...

98 Chapter 3 3.12.6 Outdoor Acoustics If, for example, the ambient noise level measured 70 dBA (not an unreasonable reading outd ...

Acoustic Environment 99 0 50 100 Distance (ft) 16 8 Noise Noise Arbitrary loudness units Figure 3.9 : Sound from an orchestra en ...

100 Chapter 3 0 50 100 Distance (ft) 16 4 Noise Noise Arbitrary loudness units Figure 3.10 : Sound from an orchestra enclosure w ...

Acoustic Environment 101 The Greeks built their amphitheaters to take advantage of these acoustical facts: They provided a back ...