There is a significant portion of the general public who have a hearing impairment at some level. The percentage of persons with hearing loss at some level increases significantly with age. As we consider the impact on the listeners in a public meeting venue we must address a solution from several angles.
First, we must consider what is actually happening that makes a person not understand what is being spoken. The major consideration is the ability of the hearer to decipher consonants which makes a significant portion of the words we speak take on meaning. For example, the words bad or back or bat are extremely similar except for the very last sound, which makes up the real meaning of the word. The last sound is a hard sound and lasts for only a millisecond. Another term for these hard sounds is sibilant. Sibilant sounds are very high in the audible frequency spectrum and, significantly, the very range where hearing impairment is impacted the most.
When addressing this issue in terms of a larger meeting space, such as a church or meeting room, this becomes a real issue since the sibilant frequencies are the hardest to propagate throughout a space. There are three areas of consideration when designing a room for sound reinforcement. They are as follows:
- Sound reinforcement system.
- Room acoustics, reverberation etc.
- Hearing assistance for impaired listeners.
Let’s look briefly at each of these areas:
Sound reinforcement. For the sibilant frequencies in the room to be pushed to each listener in the room consideration must be made to provide a loudspeaker and speaker array design capable of delivering the frequencies to each seat. The sound must arrive only once at that location at a level that is audible with secondary sound arriving at a significantly lower volume level. Proper design of this portion of a space requires computer modeling and a professional system designer.
Room acoustics. Each space has its own acoustic characteristics and the larger the room and depending on design the more reflections, reverberation or echoes develop with sound movement in the space. AS the secondary sound arrives at the listener’s ear somewhat in time after the original sound it will conflict with the original sound making it difficult or even impossible to decipher what the original sound was. And again, this clarity problem is the most problematic in the frequency range of sibilant sounds. A study of the room’s reverberant qualities must be undertaken using computer modeling and strategically placed acoustic modification must be undertaken. This generally takes the form of acoustic damping panels but can also include several other solutions. Auralex is a product specifically designed to allow an engineer to apply a fix to a space.
Hearing Assistance systems. for some people the solutions above are not sufficient to allow them to participate in the service. For them a special assistance system which can amplify the sound through an earphone or hearing aid system is the only solution. These systems can use an independent radio receiver that the listener uses with an earphone to receive the sound from the microphone directly in the ear. An alternative system called a T-Coil can be used to transmit the sound through radio waves from a personal receiver directly into a T-coil hearing aid. There are also more elaborate and expensive systems that incorporate an antenna loop around a room under the floor that directly sends radio waves to the T-coil hearing aids. Williams Sound is a company who provides such systems.
A word about the Americans with Disability Act or ADA regulations. ADA web site, click here. The ADA does require that certain rooms used for public gatherings must provide an assistive listening system. Churches are exempt from the ADA requirements but many churches do provide a system for members and attendees as a courtesy and as a way to assure all persons can understand what is being said.
This article only touches the surface of the information relating to this topic so here are some additional resources for those who may need more in-depth information.
Sound Concepts is qualified and has the computer software and training to study your space and provide a solution and costs to improve the acoustic characteristic of your sound system and room acoustics. Please feel free to contact us for a free initial consultation.