---
kind: "section"
citation: "49 C.F.R. § 325.77"
title: "49"
number: "325.77"
heading: "Computation of open site requirements—nonstandard sites."
url: "https://uscodex.org/cfr/49/325.77"
---

# §325.77. Computation of open site requirements—nonstandard sites.

- (a) If the distance between the microphone location point and the microphone target point is other than 50 feet (15.2 m), the test site must be an open site within a radius from both points which is equal to the distance between the microphone location point and the microphone target point.
- (b) **Plan view diagrams of nonstandard test sites are shown in Figures 3 and 4.** Figure 3 illustrates a test site which is larger than a standard test site and is based upon a 60-foot (18.3 m) distance between the microphone location point and the microphone target point. (See [§ 325.79(b)(1)](/cfr/49/325.79.md?p=b-1) for an example of the application of the correction factor to a sound level reading obtained at such a site.) Figure 4 illustrates a test site which is smaller than a standard test site and is based upon a 35-foot (10.7 m) distance between the microphone location point and the microphone target point. (See [§ 325.79(b)(2)](/cfr/49/325.79.md?p=b-2) for an example of the application of the correction factor to a sound level reading obtained at such a site.)

## Notes

### Authority

Authority: 42 U.S.C. 4917; 49 U.S.C. 301; and 49 CFR 1.87.

### Source

Source: 40 FR 42437, Sept. 12, 1975, unless otherwise noted.