Hearing Loss and Assistive Listening Devices
Assistive Listening Devices
Problems With Hearing in Noise
Hearing loss is often managed well in quiet environments. Hearing aids work best when there is no background noise and the speaker is facing the listener. In the real world, that type of listening environment is generally not encountered. Background noise from air conditioners, large groups of people talking, road noise, etc. interferes with speech sounds.
Hearing aids do not correct hearing in the way that glasses correct vision. Hearing aids are able to amplify sound, but do not correct for any distortion in sound quality caused by damaged outer hair cells in the cochlea (inner ear). Background noise is extremely difficult for those with more severe hearing losses (more sound distortion) and for young children with hearing loss, who cannot "fill in the gaps" due to a lack of language experience.
FM Systems for Hearing Loss
FM systems are frequently used by children in educational settings to overcome the difficulties associated with background noise. Adults also benefit from the use of an FM system. FM Systems work by sending a primary speaker's voice directly to the hearing aids. The speaker's voice is elevated above the background noise, and the problem of diminishing sound quality over distance is eliminated.
There are to primary types of systems for use in educational settings:
- Sound field systems amplify the teacher's voice by approximately 10 decibels (dB) over the background noise. This system broadcasts the speaker's voice through a set of speakers, so all children in a classroom may benefit. Sound field systems are intended for children with normal hearing, and will not be sufficient for a child with significant hearing loss.
- Personal FM systems have receivers that connect to the child's hearing aids, allowing the teacher's voice to remain 15-20dB louder than the ambient background noise. Children with mild or greater levels of hearing loss will benefit from the use of a personal FM system in the classroom.
Adults and children may use FM systems outside of the classroom. FM systems may be connected with computers, television, or other audio sources. With the use of a special connection cable, most FM systems will wirelessly transmit sound so that a hearing aid user does not need to wear headphones.
FM Systems in the Classroom
Components of a Personal FM System
All personal FM systems consist of three main components:
- A microphone.
- A transmitter.
The microphone is attached to the transmitter and is worn by the speaker. The receivers fit onto a child's hearing aids via a special attachment called "boots." The boots generally attach where the hearing aid's battery door would be. Some hearing aids now have integrated FM receivers, removing the need for boots.
Television Amplification Systems
TV Amplification systems have been designed to deliver amplified sound to a special set of headphones or to hearing aids or a cochlear implant (depending on the amplifier). These systems will allow the user to listen at a comfortable and intelligible volume without having to increase the volume on the actual TV set.
Healthcare providers with hearing loss must be able to hear heart beats and lung sounds. Many stethoscopes have been developed to amplify the sound 30 times greater than a traditional stethoscope. Visual displays are available on some models, allowing a hard-of-hearing doctor or nurse to find the location of a heart murmur or lung problem.
Induction Loop Systems
Loop systems are cheaper than personal FM systems, and may be an affordable option for houses, churches, and businesses. Loop systems typically work with a hearing aid's telecoil function, and are also compatible with cochlear implants.
Loops vary in cost, with small-scale versions starting at around $250 and large, satellite based systems starting in the $800 range. People without hearing aids cannot use a loop system unless they wear headphones with an induction receiver, and those with hearing aids must have their telecoils activated to use a loop system.
Personal amplifiers are low-cost sound amplification device. Some people purchase these systems instead of hearing aids. Personal amplifiers are not adjustable by frequency, so sound volume is simply increased across the board. These devices often double or triple the volume from an audio source. Headphones or smaller on-the-ear receivers are used for these devices.
In general, personal amplifiers have extremely low customer satisfaction ratings. As hearing loss is unique to each person and the level of loss may vary by the sound frequency (low or high pitch), a licensed audiologist should perform a hearing exam for any person who feels they cannot hear clearly. If needed, digital hearing aids may be obtained and programmed specifically to an individual's needs.
Hearing on the phone is a particular challenge for people with a hearing loss. Telephones only transmit sound frequencies below 3,000Hz, which leaves out many critical high frequency sounds. This is why people with normal hearing often have to clarify names and spelling information on a phone - "is that f as in fox or s as in sam?" The problem compounds when there is a pre-existing hearing loss.
Some phones will work with a hearing aid's telecoil feature to enhance sound quality. Other phones simply amplify sound, allowing a phone's ring to be heard by a hard-of-hearing listener. Amplified phones often increase incoming sound by approximately 50dB, allowing those with a moderate hearing loss to converse with greater ease.
Sonic Boom Alarm Clock
Hearing an alarm clock ring is a particular challenge - most traditional models are simply not loud enough. Vibrating alarm clocks solve this problem: the alarm clock has a vibrating disk that fits under a pillow or mattress. When the alarm goes off, the bed shaker activates, literally shaking the sleeping person awake.
Sonic Boom is a highly recommended alarm clock for those with hearing loss. The alarm sounds audibly at up to 113dB, and pulsating lights coordinate with the bed shaker. This system will wake anyone up, even from the deepest sleep!
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