HIS 110: Acoustics & Psychoacoustics

Beth Fernandez, AuD, CCC-AAdjunct Instructor

Ozarks Technical Community College

The REALLY important stuff…

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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

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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