Handbook for Sound Engineers

Acoustical Treatment for Indoor Areas 117

basic sense, diffusion can be thought of as a special form
of reflection. Materials that have surface irregularities on
the order of the wavelengths of the impinging sound
waves will exhibit diffusive properties. Ideally, a diffuser
will redirect the incident acoustical energy equally in all
directions and over a wide range of frequencies.
However, it is often impractical to construct a device that
can diffuse effectively over the entire audible frequency
range. Most acoustical diffuser products are designed to
work well over a specific range of frequencies, typically
between 2 and 4 octaves above roughly 500 Hz. Of
course, just as with absorbers, one must be concerned
with the performance of a diffuser.

5.3.1 Diffuser Testing: Diffusion, Scattering, and

Coefficients

The performance of a diffuser can be expressed as the

amount of diffusion and as the amount of scattering

provided by a surface. While there is still some disagree-

ment as to diffusion nomenclature, Cox and D’Antonio

have attempted to establish a distinction between diffu-

sion and scattering, particularly as it relates to the coeffi-

cients that are used to quantify diffuser performance.^2 In

general, diffusion and the diffusion coefficients relate to

the uniformity of the diffuse sound field created by a

diffuser. This is most easily explained by looking at polar

2.5 cm (1s) Roxul RockBoard 40 4-9 0.07 0.32 0.77 1.04 1.05 1.05 Ref. 17

3.8 cm (1½s) Roxul RockBoard 40 4-9 0.18 0.48 0.96 1.09 1.05 1.05 Ref. 17

5.1 cm (2s) Roxul RockBoard 40 4-9, 4-10 0.26 0.68 1.12 1.10 1.03 1.04 Ref. 17

Material Fig. 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz Source

7.6 cm (3s) Roxul RockBoard 40 4-9 0.63 0.95 1.14 1.01 1.03 1.04 Ref. 17

10.2 cm (4s) Roxul RockBoard 40 4-9 1.03 1.07 1.12 1.04 1.07 1.08 Ref. 17

5.1 cm (2s) Roxul RockBoard 35 4-10 0.26 0.68 1.14 1.13 1.06 1.07 Ref. 17

5.1 cm (2s) Roxul RockBoard 60 4-10 0.32 0.81 1.06 1.02 0.99 1.04 Ref. 17

5.1 cm (2s) Roxul RockBoard 80 4-10 0.43 0.78 0.90 0.97 0.97 1.00 Ref. 17

2.5 cm (1s) Tectum Wall Panel 4-11 0.06 0.13 0.24 0.45 0.82 0.64 Ref. 18

3.8 cm (1½s) Tectum Wall Panel 4-11 0.07 0.22 0.48 0.82 0.64 0.96 Ref. 18

5.1 cm (2s) Tectum Wall Panel 4-11 0.15 0.26 0.62 0.94 0.62 0.92 Ref. 18

5.1 cm (2s) Auralex Studiofoam Wedge 4-13, 4-14 0.11 0.30 0.91 1.05 0.99 1.00 Ref. 19

5.1 cm (2s) Auralex Studiofoam Pyramid 4-13 0.13 0.18 0.57 0.96 1.03 0.98 Ref. 19

5.1 cm (2s) Auralex Studiofoam Metro 4-13 0.13 0.23 0.68 0.93 0.91 0.89 Ref. 19

5.1 cm (2s) Auralex Sonomatt 4-13 0.13 0.27 0.62 0.92 1.02 1.02 Ref. 19

5.1 cm (2s) Auralex Sonoflat 4-13 0.16 0.46 0.99 1.12 1.14 1.13 Ref. 19

5.1 cm (1s) Auralex Studiofoam Wedge 4-14 0.10 0.13 0.30 0.68 0.94 1.00 Ref. 19

5.1 cm (3s) Auralex Studiofoam Wedge 4-14 0.23 0.49 1.06 1.04 0.96 1.05 Ref. 19

5.1 cm (4s) Auralex Studiofoam Wedge 4-14 0.31 0.85 1.25 1.14 1.06 1.09 Ref. 19

2.5 cm (1s) SONEXmini 4-15 0.11 0.17 0.40 0.72 0.79 0.91 Ref. 20

3.8 cm (1½s) SONEXmini 4-15 0.14 0.21 0.61 0.80 0.89 0.92 Ref. 20

5.1 cm (2s) SONEXclassic 4-15 0.05 0.31 0.81 1.01 0.99 0.95 Ref. 20

7.6 cm (3s) SONEXone 4-15 0.09 0.68 1.20 1.18 1.12 1.05 Ref. 20

Pegboard with 6.4 mm (¼s) holes on 2.5 cm (1s) centers

over 2.5 cm (1s) thick Owens-Corning 703

4-25 0.08 0.32 1.13 0.76 0.34 0.12 Ref. 15

Pegboard with 6.4 mm (¼s) holes on 2.5 cm (1s) centers

over 5.1 cm (2s) thick Owens-Corning 703

4-25 0.26 0.97 1.12 0.66 0.34 0.14 Ref. 15

Pegboard with 6.4 mm (¼s) holes on 2.5 cm (1s) centers

over 7.6 cm (3s) thick Owens-Corning 703

4-25 0.49 1.26 1.00 0.69 0.37 0.15 Ref. 15

Pegboard with 6.4 mm (¼s) holes on 2.5 cm (1s centers

over 10.2 cm (4s) thick Owens-Corning 703

4-25 0.80 1.19 1.00 0.71 0.38 0.13 Ref. 15

Pegboard with 6.4 mm (¼s) holes on 2.5 cm (1s) centers

over 12.7 cm (5s) thick Owens-Corning 703

4-25 0.98 1.10 0.99 0.71 0.40 0.20 Ref. 15

Pegboard with 6.4 mm (¼s) holes on 2.5 cm (1s) centers

over 15.2 cm (6s) thick Owens-Corning 703

4-25 0.95 1.04 0.98 0.69 0.36 0.18 Ref. 15

Table 5-3. Absorption Data for Common Building Materials and Acoustical Treatments (All Materials Type A
Mounting Unless Noted Otherwise) (Continued)