Understanding the Hearing Aid Candidate

Problems faced by adults with hearing impairment

#1 definitive reason was financial
The interesting thing that is brought up is that the family receives considerable benefit
- "you may have a hearing loss but your family has a hearing problem."
- communication is rendered less rewarding with a family with someone with hearing loss
SRTs and UCLs measure the dynamic range of a persons hearing
- you can do UCL for a tone
dynamic range is collected from pure tone assessment
example, if have a dynamic range of hearing at 4Khz of 20dB
- level of hearing is at 80dB and UCL is at 100dB - 20dB dynamic range
- someone will talk and the person won't hear, will raise voice and still won't hear, will yell and because of the dynamic range will feel like yelling; very limited range
- a hearing aid will treat soft sounds different in this frequency range and how it's going to treat different levels of sounds; soft sounds a little bit, medium sounds a lot
a hearing aid will aid in the clarity for someone who is able to hear but not understand
frequency resolution is really important when talking about environments
for a vowel, it's partly a first formant but then it's a second formant, which could be missing too, could be more difficult to pick missing information because of frequency loss

Percentage of U.S. Citizens with Hearing Loss by Age

Decreased Audibility

Hearing-impaired individuals cannot hear sounds that are below their threshold
for speech it can be different depending on the intensity of the speech sounds
hearing in the low frequencies
hearing the high frequencies
distance from the speaker
the ear typically identifies the peaks in the spectrum to identify the sound

Decreased Dynamic Range

the amount of sound between the threshold of hearing and threshold of discomfort
in normal hearing adults it is typically 80-100dB
reduced in hearing impaired individuals due to
- increased threshold
- abnormal growth of loudness

Frequency Resolution

the ability of the system to analyze a sound into its component frequency
- the more "fine tuned" a system, the greater number of frequencies analyzed, the better its frequency resolution
- frequency selectivity
frequency resolution plays an important role in separating speech from background noise

Decreased Frequency Resolution

With Cochlear Hearing Loss

Flatter tuning curves
poor frequency resolution
poor speech discrimination
poor speech and distracter separation
with reduced frequency selectivity
- intense low frequency components may mask lower intensity high frequency components
- this is known as upward spread of masking
poor frequency resolution at high intensities
hearing impaired listeners are listening at high intensities to compensate for poor audibility

Temporal Resolution

temporal resolution refers to the ability to represent information in the time domain
envelope
- envelope is the slower content
fine structure
- relatively fast - reflects spectral components of sounds in the sound waveform, and periodicity

Decreased temporal resolution

hearing loss can result in deficiencies in coding the temporal information accurately
the temporal fine structure is not preserved
temporal cues are distored
temporal cues in speech
- voice onset time
- formant transitions
- periodicity

Temporal Masking

intense sounds can mask weaker sounds
- that come after them or that come before them

In Hearing Impaired adults

increased temporal masking reduces sensitivity to soft sounds after an intense sound
- e.g. VC syllable Ash vs As
In the presence of background noise
- normal hearing adults can listen in the gaps
- hearing impaired adults cannot make use of the gaps
- difficulties increase in the presence of background noise

How would we help in the clinic?

How would we affect speech in noise?

directional microphones, whatever we can do to get a better speech in noise performance