Post on 19-Jun-2015
description
HIS 110: Acoustics & Psychoacoustics
Beth Fernandez, AuD, CCC-AAdjunct Instructor
Ozarks Technical Community College
The REALLY important stuff…
BALLAS ENT CONSULTANTS
Otolaryngology Head & Neck Surgery
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ENOUGH ABOUT ME!
Overview... Involved Professionals:
Audiologist Hearing Instrument Specialist Family Physician Otolaryngologist/ENT Specialist Speech-Language Pathologist
Hearing Loss
The 3rd most common health problem in the United States
36 million Americans have hearing loss (NIDCD)
1/3 of Americans aged 65 to 74 1/2 of Americans over the age of 75
Most hearing loss is due to: Aging Genetics Noise exposure!!!
Diagnostic Testing Audiogram
Tone testing, Speech testing, and middle ear testing
The goal is to determine How well you hear How clearly you hear speech If there is a medical reason for hearing loss If there is a need for some sort of intervention
Hearing Loss is defined by… Degree of Loss
Normal, mild, moderate, severe, profound Configuration of Loss
Flat, sloping, precipitous, rising, etc. Type of Loss
Conductive Sensorineural Mixed
Other Important Factors
Onset Prelingual (<5) Postlingual (>5) Deafened Hard of hearing
Speech Recognition Ability
Degree of Hearing Loss (PTA in dB)
Slight – mild 21 – 40
Mild to moderate 41 - 55
Moderate 56 - 70
Severe 71 - 90
Profound >90
Configurations of Hearing Loss Flat Sloping Precipitous
Type of Hearing Loss
Conductive Sensorineural Mixed
Causes of Conductive Hearing Loss
Outer ear infection Middle ear infection Otosclerosis Dislocation of the middle ear bones Cholesteatoma Ear wax!
Conductive Hearing Loss
Causes of Sensorineural Hearing Loss Aging Noise Exposure Genetics Acoustic Neuroma Meniere’s Disease Ototoxic Drugs
Sensorineural Hearing Loss
Mixed Hearing Loss
www.asha.org
Other Types of Hearing Loss
Functional Central auditory
processing disorder
So…how do we treat hearing loss?
Conductive Hearing Loss Medically Surgically Amplification
Sensorineural Hearing Loss Hearing Aids Hearing Assistive Technology Cochlear Implants
NOW ON TO ACOUSTICS…
What is sound?
Physical sense disturbance of molecules that is propagated
through some elastic medium, like the air Psychological sense
the act of hearing something
Acoustics Physical properties of a sound that can be
measured frequency Intensity wavelength
Psychoacoustics
Our human perceptions of sound Pitch Loudness
Frequency How often an event occurs over some
period of time
When referring to sound, frequency is defined as cycles per second unit of measurement is the hertz (Hz)
Our human ear can detect frequencies ranging from 20-20,000 Hz
Humans most sensitive hearing frequencies are from 500Hz to 5000Hz
Intensity The distance from the point of rest that
particles move after the onset of a sound Also referred to as amplitude The decibel (dB) is the most common unit
of measurement for sound intensity The human ear can detect intensities from 0 to
140 dB SPL (sound pressure level). At 0 dB, sounds are just barely audible, and at 140 dB, sounds are truly painful
Th
e D
eci
bel
Sca
le
Wavelength See dry erase board
Pitch Pitch is the subjective perception of how
“high” or “low” a sound is Pitch is directly related to the frequency of
a sound lower the frequency, the lower the pitch The intensity of a sound also contributes
somewhat to our perception of pitch.
Loudness Loudness is the psychological perception
of how “loud” or “soft” a sound is Loudness is directly related to intensity
lower the intensity, the softer the sound duration and frequency of a sound also
contributes to our perception of loudness
Other Acoustic Phenomena
Sound Localization Masking
Localization Ability to determine which direction a
sound Requires symmetric hearing in both ears
the brain uses the arrival time at the ears and the intensity level at each ear
It is very important for individual’s with hearing loss in both ears to be fit with bilateral hearing aids in order to preserve the ability to localize to sound.
Masking The ability of one sound to be “covered
up” by the presence of another sound Masking is measured by the number of
decibels the threshold of hearing is raised The softest level of noise which renders
the signal inaudible is referred to 0dB effective masking level Environmental masking Audiometric masking
Upward Spread of Masking Low frequency sounds mask or “cover up”
sounds that are of a higher frequency
Masking Backward Masking
when the signal is masked by a sound that is presented after the intended signal
Forward Masking when the signal is masked by a frequency that
is presented immediately before the signal.
Audiometric Masking Goal: to isolate the test ear and prevent
“crosstalk” between the ears
Narrowband noise Used for puretone testing
Wideband noise Used for speech testing