The following nomogram allows you to go directly from the calculated value of TI to either the Sound Attenuation or the Access Factor, both at 10,000 Hz.

Figure 23. Nomogram for calculating the Attenuation and the Access Factor (10 kHz)

The procedure is as follows:

Enter the lower horizontal scale with the value of TI for your perforated sheet and move directly upward to intersect the lower of the two curves. Move (to the left from this intersection point until you strike the vertical scale, where you can read the attenuation at 10,000 Hz in decibels.

Alternatively, if you want the Access Factor, you can move to the right or left from the first intersection point to intersect the upper slanting line, then move upward from the second intersection point to strike the upper horizontal scale, where you can read the Access Factor at 10,000 Hz for the perforated sheet. (See Example 8, next page.)