Re: Assisted Listening Device for church
As for speech levels, the dynamics of speech require you to peak at 85db, or the average level is not loud enough. Above 85 db the ear tightens and goes into compression to protect itself. Maximum intelligibility happens just below this level. So, setting 85db as your peak level for speech is exactly the right call.
The chart James attached shows that speech recognition increases as the level of the stimulus above above one's Speech Reception Threshold (SRT) increases and that while the increase in speech recognition tends to level off when the stimulus level is 30dB or so above the SRT for those with 'normal' hearing, it continues to rise for those with hearing impairments. One should recognize that the Speech Reception Threshold varies for individuals and that this chart is based on audiometric testing conditions, thus it is not directly addressing how changes in level relate to intelligibility in a space, which can be affected by ambient noise levels, room acoustics, etc. When addressing intelligibility in a church it is probably more directly relevant to consider the effects of signal-to-noise ratio and the acoustical environment.
I'm not sure clear on where the 85dB level noted (which should be noted is unweighted SPL and not A-weighted SPL) comes from. From an audiology perspective, apparently ANSI defines a normal, healthy SRT of 19dB, so 85dB would be over 65dB above that, which seems greater than needed. I've also seen references to the overloading noted occurring at 80dB with changes to phonetics and intonation starting at 75dB. From a sound reinforcement perspective, normal conversational speaking level is around 60-70dB with a 12dB crest factor (I'm assuming that "85dB as your peak level" references the peak level in terms of relating to the average level and crest factor not normal variations in level over some time or between people or the time constant of the measurement) so say an average 77dB peak level. So 75 to 80dB seems perhaps a more reasonable value.
I guess one could use the upper 70dB level for conversation and a 15dB crest factor to derive the 85dB level, however that seems to be pushing the envelope for normal speech and potentially runs into a problem I've encountered that while any additional signal-to-noise ratio may help with intelligibility, that may have to be balanced with the goal of the audio system recreating the natural sound for the listeners.
The architecture supports early reflections for maximum intelligibility and has none of the late reflections that impair intelligibility. No absorption panels needed.... This building supports amplified and acoustic speech, amplified and acoustic music, and congregational acoustic speech and music. When a building supports all 6 kinds of sound sources, it's really a beautiful thing.
As the uses noted represent a rather wide and disparate range of desired acoustical conditions, do you mean that the acoustical environment can be adjusted for different uses or that some 'best fit' balance of compromises was made?
I stand by my statement, In most cases, if your intelligibility or %alcons is where it needs to be for church, hearing assistance is not needed, and an individual persons hearing devices (aids) will be sufficient. Fixing the room should always be the first goal.
Agree fully with the last comment, but the first may be a bit unrealistic. One issue is that not all hearing impaired people have the same hearing loss and not all hearing impaired people use hearing aids. I have had clients tell me to plan on accommodating audience members with hearing loss but that will not use hearing aids. Another rather common situation is that while most churches may not have to comply with ADA, some do and many more choose to, which means that ALS is then an integral part of that compliance.
