What are the advantages and disadvantages of using induction loops versus digital wireless hearing aid accessories to improve hearing in multiple listening environments?
Telecoils have been used in hearing aids for a long time. The main advantages of telecoils include blocking environmental noise and improving the signal to noise ratio – all without the risk of acoustic feedback. One of the most common applications of telecoil use is for the telephone. By receiving the electromagnetic signal directly from the telephone handset without the activation of the hearing aid microphone, there is no chance of feedback. At the same time, this transmission reduces the level of environment noise for the listener, and makes it easier for the user to concentrate on the conversation.
Telecoils are also advantageous for use with loop systems in large, public venues where listening may be exceptionally difficult. These environments are typically characterized by background noise, reverberation, and significant distance of the listener from the sound source. When a loop system is installed in a venue such as a church or theater, the broadcasted sound will be sent directly to the hearing aids via the telecoil, thereby improving the signal to noise ratio. Telecoils are advantageous in these looping environments due to their ease of use, with no pairing required to tap into the broadcasted signal. The telecoil program can be activated by a simple press of the program button or by switching to the telecoil (T) setting. Adding to the attractiveness of telecoils is their relatively low cost.
So, is there a catch? Like most kinds of technology, there are situations which may be more advantageous or disadvantageous for telecoil use. First, telecoils are optimized for speech signals, so music may sound distorted. This is due to the fact that music is often comprised of higher frequencies than the telecoil bandwidth can handle. Second, the orientation of the telecoil is important to achieve a good signal with the telephone or in a looping environment. Telecoils obtain the best signal when they are oriented at a 90 degree angle from the loop or coil. Thus, telecoils are best oriented horizontally for telephone use and vertically for looping systems. Depending on the orientation of the telecoil in the hearing aid, the user may need to position the telephone handset differently in order to get the best signal. Third, the use of telecoils in venues necessitates installation of a fixed loop in that space. The loop cannot be easily moved to other locations, and the signal strength is limited to the confines of the loop. For example, if the loop is installed for a TV in the living room, when the user leaves the living room the signal strength will decrease dramatically. Lastly, loop systems may experience interference from other electronics, which can be perceived by the hearing aid user as a buzzing sound.
In recent years, digital wireless hearing aids and accessories have become more and more popular. One of the main advantages of digital wireless technology is that it renders more options for phone use than were previously available. Digital wireless communication between hearing aids in a binaural pair has led to features such as ReSound’s Comfort Phone, which reduces the hearing aid gain for the non-phone ear. This automatically decreases ambient noise, making it easier for the user to focus on the phone conversation. Another advantage of digital wireless technology is the possibility of streaming the phone signal to both hearing aids simultaneously. Recent research indicates that binaural streaming of the phone signal results in better speech recognition performance and improved listening ease and comfort, as compared to monaural listening via telecoil (Picou & Ricketts, 2013).
Digital wireless technology enables hands-free communication abilities on the phone, and ensures privacy due to the precise pairing protocol necessary for connection to the hearing aids. In addition, the wider frequency response and low likelihood of interference enables digital wireless hearing aid accessories to provide excellent sound quality for both speech and music. Binaural streaming of music from the phone directly to the user’s hearing aids is a reality with this technology.
Disadvantages of digital wireless technology include its relatively higher cost as compared to telecoil technology. Further, there is no common standard for digital wireless transmission in large public venues, as different hearing aid manufacturers may use different digital wireless technology. Finally, the accessories need to be paired to the hearing aids, which may cause a certain degree of inconvenience.
Both telecoil and digital wireless technology have distinct advantages and disadvantages. In certain situations, one type of technology will be preferred. Fortunately, telecoil and digital wireless technology are not mutually exclusive. Both types of wireless technology can be incorporated in most modern hearing aids, allowing the user to more fully enjoy the benefits of improved signal to noise ratio in various settings.
Picou, E.M., & Ricketts, T.A. (2013). Efficacy of hearing-aid based telephone strategies for listeners with moderate-to-severe hearing loss. Journal of the American Academy of Audiology, 24(1), 59-70.