What is a Sound Field Amplification System?

A sound field amplification system is used in the classrooms to improve the signal-to-noise ratio, amplifying the teacher’s voice above the ambient noise in the room.  The sound field amplification system consists of:

  • a microphone/transmitter
  • an amplifier and
  • a number of strategically placed loudspeakers in different locations around the room and ceiling (Crandell and Smaldino, 2002). 

This system is useful for students with mild or fluctuating hearing impairment (e.g. caused by Otitis Media) or central auditory processing disorder.

How Does a Sound Field Amplification System Work?

The teacher wears a microphone and radio transmitter that transmits their voice to speakers installed in the classroom.  It provides amplification uniformly throughout the classroom.  There are also portable sound field systems which can be placed on the student’s desk (Crandell and Smaldino, 2002). 

Benefits of Sound Field Amplification Systems

Sound field amplification systems have been demonstrated to improve the learning environment for students and teachers due to the following:

  • they can be used with students with mild hearing impairments and fluctuating hearing impairment
  • they improve the signal-to-noise ratio for all students in the class (Lewis, 1998)
  • no receiver is required
  • they enable teachers to be mobile, aid teachers with projecting their voices and thereby avoid vocal abuse (Crandell and Smaldino, 2002)
  • They improve the learning environment for the student by enhancing speech perception.

It is important to note that the other assistive listening devices described in this section may be more relevant for students with severe hearing impairments, because the sound field amplification system does not provide enough amplification relative to the degree of hearing loss (Lewis, 1998).   Also, a sound field amplification system will not provide adequate benefits in excessively noisy or reverberant environments (Crandell and Smaldino, 2002).

Tips for Teachers Using Sound Amplification Systems

  • Every classroom is different in terms of its size, shape, seating arrangements and teaching style used (Lewis, 1998).  It is important to take these factors into consideration when deciding on the loudspeaker arrangements or number of loud speakers in the classroom (Crandell and Smaldino, 2002).  Lewis (1994) states that inappropriate installation may result in an amplified signal that is poorer than the un-amplified signal. 
  • Audiologists recommend the use of sound field amplification systems (Flexer, 1997) based on an evaluation of classroom acoustics such as ambient noise level, reverberation time and signal-to-noise ratio. Based on the measurement results, audiologists then select, evaluate and customize sound field systems to fit the needs of the students, teachers and classroom.
  • It is not practical to move the system from one classroom to another so its location needs to be carefully considered.