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Sound Enhancement Systems: Description & Rationale

Research has found that a student’s ability to learn and academic performance are negatively affected when the teacher’s ability to verbally communicate is blocked or muddled by overwhelming background noises. It is crucial for students to hear what the instructor is saying in order for effective learning to take place. Therefore, since we cannot do anything to speed-up the development of children’s auditory abilities, nor reduce the number of “at-risk” students, it is abundantly clear that we must do something to either improve or compensate for the poor acoustics.

It would seem logical that the best solution for overcoming the adverse effects of noise would be to attenuate it at its source. Noise is controlled in one of two basic ways. It is either insulated from the learning environment by some type of barrier, or it is eliminated. This is what the Acoustical Society of America has attempted to do in developing the acoustical design standards under the American National Standards Institute. However, there are two problems with trying to control the background noise alone.

First, it is not always fiscally feasible to retrofit/remodel every classroom with solutions designed to engineer out troubling noise. This is one reason why in 2002, the International Code Council (ICC) did not adopt the ANSI standards for inclusion in the 2003 International Building Code. It was also not adopted due to concerns over realistic attainment of those specifications. The LAUSD study validated those concerns by reporting background noise levels never dropping below 43 dBA in the occupied classroom, except during silent reading periods. Therefore, spending money to reduce the building-generated noise is nonproductive once that noise falls below the sound levels created by the students.

Second, it is impossible to eliminate background noise created by its occupants and instructional equipment, in order to reduce the background noise enough to ensure that ALL children throughout the room are achieving a Signal to Noise Ratio of +15 decibels. This was proven in the LAUSD study previously discussed. For example, the typical conversational level of a teacher’s voice is 65 dBA, which means that the background noise can theoretically be no more than 50 dBA to achieve a SNR of +15 dBA. However, this assumes that all students are within a normal conversational distance to the teacher, so that sound is not decreasing over distance. (Remember that sound decreases 6 dBA for every doubling of distance.) We know that a classroom set-up allowing all students to be within 2-3 feet of the teacher is impossible. Children are seated throughout the classroom, staggered over the distance of the room, more than conversational distance from the teacher. Beyond 8 feet from the teacher, the teacher’s voice will be heard at less than 47 decibels, which produces an SNR of negative 3 dBA (47dBA minus 50dBA), not enough for students to hear and fully understand what is being spoken.

Therefore, the only feasible way to overcome this barrier is to bring the teacher’s voice at 65 decibels, closer to each student, including those in the back row. This is the rationale behind the classroom sound enhancement system, which creates a front-row seat for every child in the classroom. The classroom sound enhancement system works by picking up and amplifying the teacher’s voice (8-10 decibels) from a wireless microphone and distributing it through four to six ceiling speakers strategically placed throughout the classroom. With students sitting no more than 10 feet from one of the ceiling speakers, this allows every student the acoustical advantage of sitting in the front row and ensures that ALL students achieve a signal to noise ratio of +15 decibels, at a minimal cost of $1500 per classroom.

The initial generation of sound enhancement systems employed a FM radio signal for the wireless microphone. This is still widely utilized and, for some types of situations, this is the system of choice. However, the dependency on limit FM frequencies greatly restricted widespread use of this technology in more urban environments. Beginning in the 1990’s, Infra-Red (IR) classroom enhancement systems were introduced. IR has the advantage of precluding interference between classrooms, eliminating static, and no longer restricting the number of classrooms due to restrictions in the number of frequencies.

When people hear that a sound enhancement system raises the teacher’s voice 8 to 10 decibels, people fear the “blasting” of the teacher’s voice. The common misperception is that sound enhancement systems are small public address systems which will produce an excessively loud teacher’s voice causing sound bleed-over into the adjacent classrooms. Those who believe this, either do not understand how a quality sound systems works or they have had the misfortune of using an inferior audio product that was either not installed correctly or not used correctly.

If a quality system is correctly installed, the primary benefit is in the even distribution of the teacher’s voice, not the amplification of the teacher’s voice. In fact, sound enhancement systems allow the teacher to use a conversational tone, because he/she doesn’t have to be concerned with projecting their voice to the back of the room. A teacher can actually speak in a softer more nurturing voice, which is more conducive to learning. Therefore, the 8-10 decibel increase is insignificant and does not cause any sound bleed-over. Instead, the voice is more clear, crisp and understandable regardless of the physical position of teacher and the student.

Classroom sound enhancement systems should not be identified with the personal worn FM hearing systems. Personal worn FM systems are assistive hearing devices used by hearing impaired children. They benefit only the single child using the personal device, by picking up the teacher’s voice and directing it into the ear of the hearing impaired child. They filter out the background noise. This is helpful and a necessary learning aid for the hearing impaired child, but it does not benefit the other children in the class. It also only amplifies the teacher’s voice, not the voices of the other students in the room. So, unlike the classroom sound enhancement system that offers a hand-held microphone for the children to use, the hearing impaired child cannot hear or learn from the other students talking in the room. Sound enhancement systems used in addition to personal FM assistive technology allows the hearing impaired child to hear other the students and the teacher, including the hearing impaired child as part of the class discussion.