Negating Noise

Correctional facilities are not the quietest or most serene places on earth. Sturdy concrete and steel enclosures provide security, safety and risk management, but they also sometimes create an acoustics nightmare that amplifies voices, footsteps, operational machinery and other sounds.

Concrete and steel surfaces offer a great echo chamber for sound waves, creating reverberation times that allows high noise levels. RT measures the time sound bounces through a space, it is not addressed by the current American Correctional Association’s standards for noise levels. However, that may soon change.

In January 2004, the ACA’s Facilities Design Acoustics Subcommittee presented to the full Facilities Design Committee a proposed revision of the current ACA noise standard. The current standard requires that “inmate housing units do not exceed 70 dBA in daytime and 45 dBA at night.” (70 dBA is about twice as loud as a normal conversation.) The revision includes a measurement of RT to supplement the dBA standard, and it was approved by the committee last January after a study affirmed it’s a better standard. The study’s authors are now hoping the ACA Standards Committee will review the revision and approve it this summer.

Standard Revision Premises

• Noise level standards for activities that occur outside prison spaces that are similar to those that occur day rooms are generally far quieter than the current ACA standard. The U. S. Environmental Protection Agency suggests acceptable noise levels for classrooms (40dBA), general office (50dBA) and light industrial spaces (58dBA). Keep in mind, every increase of 10dBA is a twofold increase in noise.
  
• The importance of the discrepancy between corrections areas and non-corrections workplaces is seen in a study conducted at a prison in Oshkosh, Wis. in 1995. In the study, the effect of different noise levels on correctional officers and staff in three housing units was evaluated. The results: higher noise levels in housing units were found to be correlated with more significant staff concern for safety, security and control.
  
• While there is general agreement that 70 dBA is too loud if housing units are meant to allow staff and inmates to talk in normal tones, without raised and strained voices, many experts and administrators agree this is not the only shortcoming of the dBA standard. Another key shortcoming is the lack of definition for how to measure sound. There are no accepted guidelines.

The committee asked for additional research to corroborate existing data that supports the recommendations for the new standard. Specifically, the committee sought additional support of the association between noise levels (dBA) and RT, and how noise levels affect staff and inmates. In response, independent acoustical consultant Jerry Christoff developed a field study with Knut Rostad, head of the Committee on Acoustics working group. Professor Richard Wener of Polytechnic University designed the staff and inmate survey instruments, and Steven Carter, an architect and Correctional News columnist (see page 38), provided technical assistance. The study was conducted over several months at correctional facilities in Colorado, Virginia, Maryland, Arkansas and California.

Study Methodology and Results

In order to affirm the correlation between reverberation time and the noise levels, acoustical measurements were performed in eight facility day rooms. Measurements included the reverberation time and long-term noise measurements in the occupied day rooms on two consecutive days — Friday and Saturday. A microphone was placed as far as possible from individual noise sources — talkers, televisions, etc. — along with an environmental noise analyzer. The analyzers did not record any actual speech, so the privacy of the inmates was protected.

The measurements underscore two points. First, recorded dBA measurements indicate that the sound level is not constant during day and evening times. In general, it is highest during dinner hours. This illustrates the problem with a noise standard that is based on a sound level limit, such as the current ACA Standard of 70 dBA. Since the sound level in an occupied day room is not constant, when should a measurement to establish whether the 70-dBA limit is exceeded be made and what activity should occur during the noise measurement?

Second, results show RT and dBA do correlate. In fact, there is a strong correlation between the Equivalent Sound Level— the level of a constant sound that would have the same sound energy during the two days between 4 p.m. and 9 p.m. (Friday and Saturday night) and reverberation time for each of the facilities.

The study highlights why the current ACA standard of 70 dBA should be revised. It is nearly impossible to uniformly apply the 70-dBA-noise limit. Also, that limit cannot be tested until the facility is complete. So if noise exceeds the limit, costly noise mitigation measures must be taken.

The advantage of applying a RT standard is clear. RT can be measured off drawings during the design process, or from calculations from an existing space. The calculations are straightforward. Measurements can be easily made from the room volume and the sound absorbing properties of the room surfaces using simple arithmetic.

Noise Impact on Staff & Operations

The importance of any standard is related to its impact on the safety and security of the institution and the well-being of staff and inmates. The data in the Oshkosh study suggests a relationship between noise levels (at 63, 67 and 69 dBA) and staff and inmates’ concern for noise and their feelings for safety and control. Of particular note is the issue of control. Research literature suggests feeling of lack of control increases stress. Oshkosh staff ranked noise “a significant contributor to tension or stress.” Oshkosh warden Gudmanson underscored these concerns noting, “Noise can mask aggressive behavior.”

During the reverberation time study, inmates and staff from four facilities that had RT times between 1.5 and 2 RT said they find noise annoying and stressful. The dissatisfaction with the acoustics seems to correlate with the range of acceptable RT standards for non-corrections environments of .75 to 1.5 RT. On this basis, there is a case to recommend a stricter RT standard (of .5, 1.0, and 1.5 seconds for one, two, and three tier rooms).

Conclusion

Many corrections professionals work in some of the most stressful environments imaginable. ACA Executive Director Jim Gondles noted in a recent USA Today column, that these 750,000 men and women deserve our gratitude for keeping facilities safe and secure. He might have added they deserve housing units that allow normal conversation with inmates. Reduced noise reduces stress and infractions, so the building blocks of re-entry — treatment, education, training, work — may just have a shot at taking hold. Noise control is neither liberal nor conservative. It’s normal. Don’t corrections professionals deserve this much?