Assistive Listening Devices
Assistive Listening Devices - Signal to Noise Ratio
Assistive Listening Devices (ALDs) are instruments that help to amplify auditory sounds and aid in deciphering sound, in particular, speech sounds from noise (Wendt, Quist, & Lloyd, 2011). There are many different types of assistive listening devices with the intention of bringing the sound closer to the listener. Some, such as hearing aids, are electronic amplifying devices that can be attached to the ear (behind, in or in the canal of the ear). Examples of other types of devices are amplifiers for speech or when using the telephone, FM (frequency modulation) systems; even television captioning is classified as an ALD (Wendt, Quist, & Lloyd, 2011). Here, more information can be found about ALDs and examples: http://www.cicada.org.au/index.php/facts-a-info/technology-to-help-hearing/59-understanding-assistive-listening-devices-alds (CICADA Australia Inc., 2012).
Technology available for people suffering from hearing loss has rapidly evolved over time. The complexity and efficiency of hearing aids, assistive listening devices and other hearing enhancers has greatly impacted upon those suffering a hearing loss. Interestingly, one of the first types of acoustic hearing aids available were ear trumpets which transmitted sounds to a higher or lower degree, depending on the trumpet itself. These were predominantly used during the 17th, 18th and 19th centuries (Stephens & Goodwin, 1984). Fully digital models of the hearing aid arose in 1996 and from then on continued to advance (Hochheiser, 2013). Like hearing aids, assistive listening devices today, are very advanced and are now very low-maintenance, small, practical and can be used in a variety of ways or in a number of different situations/settings.
As previously mentioned, ALDs help in deciphering proper sound signals from background noises, which pose a significant problem for people with hearing difficulties. This is referred to as a signal-to-noise ratio (SNR) and is predominantly measured in decibels (dB). The lower the level of signal-to-noise ratio produced, the higher the sound quality. It is important, particularly for children because they are required to learn new vocabulary and information in noisy environments, like the classroom (Nittrouer, Caldwell-Tarr, Tarr, Lowenstein, Rice, & Moberly, 2013). The study recognises that even children with no apparent hearing loss still have some issues learning when noise is not easily separated from significant sound. Thus it is vital for the two to be distinguished, particularly for those with a hearing loss.
For an overview of ALDs, you can find a detailed video here: https://www.youtube.com/watch?v=cmGbALGIS-A&list=PLywc5hkhK4WBcpwXfdPg8DRweUxDFKXxK&index=3
Loop System
Background Information
Loop systems were first introduced in the 1950s (Hersh and Johnson, 2003). For 40 years, they have been used in educational settings (assistive listening devices) and are the most common hearing aid that is wireless (Hersh and Johnson, 2003). Loop systems are used in environments with unideal listening conditions (Oyiborhoro, 2005) and a poor acoustic environment, such as reverberation and echoing (Hersh and Johnson, 2003). Loop systems can be used by both those with a hearing aid and those without (assistive listening devices). Loop systems come in two dimensional systems and three dimensional systems, two dimensions are the wire systems spread in the room, whereas three dimensional systems uses mats instead. (Warick, Clark, Dancer and Sinclair, 1997).
How It Works
The main aim of induction loop systems is to relay speech signal immediately to the person with the hearing impairment, while avoiding any unnecessary noise, echoing or reverberation. (Hersh and Johnson, 2003). This is done by converting the spoken language into a microphone, which is electromagnetically sent to the individual (Oyiborhoro, 2005). The speech is transmitted to the individual through a magnetic field which is established from the loop of wire that creates an electric current, this field can be altered by using different types of metals and shapes. After the information travels through space it is picked up by a coil, and transferred back to acoustic sound for the individual (Hersh and Johnson, 2003). A signal to noise ratio of 0-15 dB, is required in hearing aid users (Hersh and Johnson, 2003).
Here is a video on a loop system set up and explaining its use: https://www.youtube.com/watch?v=JfA4sBEL8GU
Positives of Loop Systems
The main advantage of loop systems is simplicity (Hersh and Johnson, 2003). Another positive about using loop systems is that they can be used with or without a hearing aid. For those without a hearing aid, a portable induction receiver can be used instead (Warick, Clark, Dancer and Sinclair, 1997). Loop systems circumference can be altered to suit the environment. It can be extended for large spaces such as auditoriums, theatres and churches, or only to the immediate individual (Oyiborhoro, 2005). Another advantage it can be altered to suit different listening levels, for example to allow the individual to watch TV but participate in a conversation with an individual at the same time (Warick, Clark, Dancer and Sinclair, 1997).
Negatives of Loop Systems
A disadvantage to loop systems is that interference can occur, from other electronic devices (Hersh and Johnson, 2003). An issue with loop systems is that spill-over can occur. This is when electromagnetic energy passes through other parts of the room, such as the floors and walls. This can be costly to shield (assistive listening devices). Costs can also occur at installation and repairing of the system (Hersh and Johnson, 2003). Otherwise if not installed properly it can cause a safety hazard (Warick, Clark, Dancer and Sinclair, 1997).
FM Systems
Frequency Modulated (FM) systems are an Assistive Listening Device which help individuals with hearing impairments and learning disabilities to communicate, detect sounds and comprehend speech (Khal, 2014). It is a radio that operates on FM waves and consists of 3 major components: a microphone, transmitter and a receiver (Conway, 2007).
How It Works
The person in which is speaking to the hearing impaired individual, wears/holds a microphone along with a transmitter. These two components can be joined together into one convenient device. The hearing impaired has a receiver that looks similar to the microphone and also wears a neck loop which is placed around the neck (Khal, 2014). The neckloop is the actual device that sends the sound signals to the hearing aid. For this to be successful, the hearing aid must be set onto a setting known as the ‘t-coil’ setting. The FM system is constructed to increase the signal-to-noise ratio allowing for background noise to be eliminated and the focus to be primarily on the speaker. So in general, the conveying voice will be sent via the transmitter to the receiver, get picked up by the neck loop and then be delivered to the t-coil in the hearing aid resulting in the ability to hear (Gaydosik, 2013).
Advantages of FM Systems
There are many advantages to using FM systems not only for those with hearing impairments but also people with learning disabilities, attention deficit disorders (ADD) and children who get distracted and lack focus especially in the classroom (Gaydosik, 2013). Firstly, FM systems can be used productively in a wide range of settings such as lecture halls, classrooms, auditoriums, theatres and churches for example (Nguyen & Bentler, 2011). They have the ability to reduce background noise and distractions allowing for greater focus and attention onto the speaker (Gaydosik, 2013). They also allow for the receiver to hear and clearly understand the speaker as if they were very close, even if the speaker is a fair distance away. FM systems are available at lower costs compared to other devices, are unaffected by bright light from both inside and outside surroundings, FM signals can be easily transmitted through walls and installation of these devices may only take a few minutes (Borgerson, 2004).
Disadvantages of FM Systems
Although there are numerous advantages to communication and personal functioning through the use of FM systems, there are also some disadvantages. Wall penetration can be identified as problem for FM systems as signals may be transmitted beyond walls and violate privacy. There may also be the possibility of interference from other frequencies (Borgerson, 2004).
Here is a video detailing the difference in FM stimulation through hearing aids: https://www.youtube.com/watch?v=1l37lzLIgQU
Assistive Listening Devices in Education
Implementation of Assistive Listening Devices in the Classroom
It is not uncommon for hearing impaired children to be assimilated into mainstream schooling (Power & Hyde, 2002). It is therefore vital that the learning environment is suitable for students that are hearing impaired, extinguishing any barriers that may create inequities in the classroom (Power & Hyde, 2002). For example, schools may need to develop classrooms to have amplification systems, a form of assistive learning device that links teachers to their hearing impaired students (Seale, 2013). It may also be beneficial to have a real time verbatim transcription system available in schools to allow hearing impaired students to receive immediate subtitles on the teacher/student dialogue, however these systems are expensive and require skilled operators (Wald, 2002). Computers are also an effective assistive learning device that assists children with hearing impairment (Wald, 2002). Computers are helpful as students have the ability to type notes rather than write, therefore minimising the extra time hearing impaired students may need to handwrite tasks (Wald, 2002). A computer or laptop would also have additional supportive software available, such as speech recognition that would assist in electronic note taking (Wald, 2002). Furthermore, schools need to consider the safety of hearing impaired students, thus, warning signs, such as fire alarms, need to be modified with flashing lights and vibrating pages so that everyone is aware of the alert (Swann, 2009). It is evident that school developers need to consider assistive learning devices that support students with hearing difficulties and design acoustically treated rooms to eliminate the inequality hearing impaired students face in attaining an education.
In addition to creating a supportive environment, it is also paramount that teachers are equipped for teaching a range of students with varying requirements and levels of learning. There are many teaching methods that assist hearing impaired students, these include:
- Recording lessons and superimposing subtitles in the recording (Wald, 2002)
- Provide assistance and additional time for note taking or provide student with notes prior to teaching (Wald, 2002)
- Be aware that some hearing impaired students rely on lip reading and therefore always face students and have well lit classrooms (Swann, 2009)
- Moderate volume to a suitable level for children with hearing aid devices (Swann, 2009)
- Learn and use sign language (Swann, 2009)
With careful consideration, funding and understanding, classrooms can be modified to contain certain assistive learning devices what will help in the education of a hearing impaired child or adult. With a proper education, people with hearing impairments will have the skills to work and actively participate in their community. For further explanation of how to effectively implement an FM system in the classroom visit: http://www.youtube.com/watch?v=ln8NHzVfJkQ
Benefits of Assistive Listening Devices in Education
There is a high level of noise in preschool. The large amount of background noise is amplified by hearing aids, which makes it difficult for children with a hearing loss to understand and participate. But with the appropriate assistive listening device, a child with a hearing loss can participate in lessons and play on the same way as his or her classmates who have normal hearing (Hersh & Johnson, 2003).
Assistive listening devices (ALDs) come with many benefits to children with hearing loss and also for children that do not have a hearing loss. Assistive technology listening devices play a vital role in students’ learning environments. The use of devices such as loop systems and FM systems in the classroom has improved the achievements of hearing impaired children both academically and socially in the school environment. According to Alodail (2014) within learning environments ALDs serve an important role between students and teachers by allowing both groups to get information that would be unavailable otherwise.
Some of the benefits include:
- The microphone location allows the level of teachers voice to remain constant to the student irrespective of the distance between them.
- The teachers voice will also be heard clearly over classroom noises such as chairs moving, fan motors running, and students talking.
- They will be enabled to perform to the best of their ability in a regular education program with his/her year level peers.
- ALDs can be either permanently installed in a classroom but they can also be moved from class to class if that is a requirement. Hence the student has the support of the device in any classroom setting.
- They can also be very helpful when working in small groups or as a whole classroom.
- ALDs are also beneficial for students with varying degrees of hearing ability, ranging from normal hearing students to students with profound hearing loss. Therefore the benefits are not only apparent for students with hearing loss but also for a student with normal hearing that has other learning requirements such as a student with central auditory processing disorder or attention deficit disorder.
- The devices can also be used in conjunction with personal hearing aids and cochlear implants which allows for students to gain additional support in amplification of sounds in potentially noisy classrooms.
- ALDs can also be very useful for students when listening to audiovisual equipment such as DVD’s and stereos (National Technical Institute for the deaf, 2014).
Alerting Devices
There are two major categories of assistive learning devices (ALDs): listening devices and alerting devices. Listening devices are the more traditional devices to help amplify sound such as those already discussed like the FM system and loop system, whereas alerting devices use vibrations and flashing lights as an indicator of environmental cues (Khal, 2014). While the listening devices assist in communication, alerting devices provide more independence and management in daily life. For some common assistive listening and alerting devices and their solutions, please follow this link : http://0-www.magonlinelibrary.com.alpha2.latrobe.edu.au/doi/pdf/10.12968/bjha.2009.3.10.44579
There are plenty of alerting systems available to those who are hearing-impaired or deaf. Common devices include those alerting to danger or environmental cues such as smoke alarms, hearing a doorbell or a baby cry and alarm clocks. Each of these devices uses a combination of high decibel alarm tones, vibrations and/or flashing lights to maximise independent living (Swann, 2009). Examples of these devices can be found here: http://www.deafblindinformation.org.au/acquired-deafblindness/equipment-assistive-devices/alerting-devices
An example of an alerting device is the Sonic Boom Alarm Clock, designed specifically for the hearing impaired or deaf. As seen in the video, it utilises loud sounds, flashing lights and a vibrating pad placed under the mattress to assist in waking up without the use of conventional alarm clocks. Alongside this, there are also uses of flashing lights to act as a doorbell (Figure 1). The lights can be set up in visible areas of the home, or can be alerted through a transmitter worn on the clothing. In most instances, these devices are single faceted, in that each device is responsible for a single service. Though, some devices are able to combine multiple alerts, such as the doorbell, baby monitor, fire alarm and telephone, into one, meaning the user would simply wear a transmitter which would vibrate if any of these were activated. It is devices such as this which allows for hearing impaired and deaf people to live independently, able to complete household activities such as waking up on time for work and knowing when someone is at the door. A video detailing the use of the Sonic Boom alarm clock can be found here: https://www.youtube.com/watch?v=XSyLFniDfSY
When it comes to alerting devices, there are three types of design principles which can be adapted:
- Design for all
- Design specifically for deaf and hearing-impaired people
- Modification of devices designed for hearing people to be used by deaf and hearing-impaired people
Design for all, also known as universal design, has the most benefits and therefore is the preferred approach (Hersh & Johnson, 2003). Though not the current case, pushes in new legislation may see the shift from the design specifically to deaf and hearing-impaired people to the universal design for alerting systems.
In combination with other listening devices such as hearing aids and cochlear implants, assistive listening and alerting devices can provide independence and maintenance of daily tasks for those who are hearing impaired or deaf.
Five Questions for the Readers
- How does sound travel from a person's mouth to a hearing aid?
- Explain how a loop system transmits sounds from the speaker to the individual.
- What is meant by signal-to-noise ratio?
- Suggest three disadvantages hearing impaired children encounter in a classroom and discuss how an assistive learning advice may alleviate the inequity.
- What are alerting devices? Name some examples and how they assist in maintaining an independent lifestyle for those who are deaf or hard of hearing.
References
Alodail, A, K. (2014). Instructing educators in the use of assistive technology listening devices in the classroom. International educational studies, 7, 55-57. Retrieved from http://0-search.proquest.com.alpha2.latrobe.edu.au/docview/1534085368?accountid=12001
CICADA Australia Inc. (2012). Understanding Assistive Listening Devices (ALDs). Retrieved September 16, 2014, from Cochlear Implant Club and Advisory Association:
http://www.cicada.org.au/index.php/facts-a-info/technology-to-help-hearing/59-understanding-assistive-listening-devices-alds
Borgerson, B. (2004). FM Assistive Listening Systems. Sound + Video Centraction, 22(1), 48-56.
Bombicino, J. (Jan 23 2011). Hearing Aid - FM simulation [Video file]. Retrieved from
https://www.youtube.com/watch?v=1l37lzLIgQU
Conway, M. (October 11 2007). FM Assistive Listening Device [Video file]. Retrieved from
http://www.youtube.com/watch?v=M4lBkdRereE
Etyhead. (2013, 10 21). Induction loop systems [video file]. Retrieved from
https://www.youtube.com/watch?v=JfA4sBEL8GU
Gaydosik, J. (April 16 2013). FM Systems in 5 minutes [Video file]. Retrieved from
http://www.youtube.com/watch?v=-aayYHyMQ8s
Hearinglossaa. (2012, November 20). Assistive Listening Technology [Video file]. Retrieved from
https://www.youtube.com/watch?v=cmGbALGIS-A&list=PLywc5hkhK4WBcpwXfdPg8DRweUxDFKXxK&index=3
Hersh, M. A., & Johnson, M. A. (2003). Assistive technology for the hearing-impaired, deaf and deafblind. London: Springer-Verlag London Limited.
Hochheiser, S. (2013, July 22). The History of Hearing Aids. Retrieved September 16, 2014, from The Institute:
http://theinstitute.ieee.org/technology-focus/technology-history/the-history-of-hearing-aids
Khal, G. (2014). Straight talk about assistive listening devices. Hearing Health Foundation (U.S), 30, 42-44.
National Technical Institute for the deaf. (2014) Assistive listening devices: The role of assistive listening devices in the classroom. Retrieved from http://www.necc.mass.edu/academics/support-services/learning-accommodations/deaf-and-hard-of-hearing-services/student-resources/accommodations-tipsheets/assistive-listening-devices/
Nguyen, H., & Bentler, R. (Oct 11th 2011). Optimising FM Systems. ASHA Leader, 16(12), 5-6.
Nittrouer, S., Caldwell-Tarr, A., Tarr, E., Lowenstein, J., Rice, C., & Moberly, A. (2013). Improving speech-in-noise recognition for children with hearing loss: Potential effects of language abilities,
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Oyiborhoro, J. M. (2005). Amplification and assistive technology. In Aural Rehabilitation of People With Disabilities (pp. 173-208). Amsterdam, Netherlands: Elsevier Academic Press.
Power, D., & Hyde, M. (2002). Deaf and hard of hearing students in Australian schools. Journal Of Deaf Studies And Deaf Education, 7(4), 302-311. Doi: 10.1093/deafed/7.4.302
Seale, J. (2013). Approaches to developing accessible learning experiences: Conceptualising est practice. New York, USA: Routledge.
Stephens, S., & Goodwin, J. (1984). Non-electric aids to hearing: A short history. International Journal of Audiology, 23 (2), 215-240.
Swann, J. (2009). Hearing impairments: problems and assistive devices. British Journal of Healthcare Assistants, 3(10), 474-478.
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Warick, R., Clark, C., Dancer, J., & Sinclair, S. (Eds.). (1997). Assistive listening devices: A report of the national task force on quality of services in the postsecondary education of deaf and hard of
hearing students. Rochester, NY: Rochester Institute of Technology, National Technical Institute for the Deaf.
Wendt, O., Quist, R., & Lloyd, L. (2011). Assistive Technology: Principles and Applications for Communication Disorders and Special Education. Bingley: Emerald Group Publishing Limited.
Submitted by Karina Allan, Leonie Flood, Sophie Keating, Renae Phillips, Michelle Le and Nicole Reinisch