Audiometry

The audiogram is a graph depicting hearing thresholds in decibels on the ordinate and frequency in hertz on the abscissa.

Audiometry includes tests of mechanical sound transmission (middle ear function), neural sound transmission (cochlear function), and speech discrimination ability (central integration). A complete evaluation of a patient’s hearing must be done by trained personnel using instruments designed specifically for this purpose. The audiogram reads in frequency (pitch) across the top or horizontal axis and it reads in decibels (loudness) down the side or vertical axis. Just like a piano’s keyboard.

The loudness scale goes from very soft sounds at the top (-10 or 0dB) to very loud sounds at the bottom (110 dB). It is important to remember that 0 dB does not mean that there is no sound at all. It is simply the softest sound that a person with normal hearing ability would be able to detect at least 50% of the time. Normal conversational speech is about 45 dB.

 Techniques:

<!–[if !supportLists]–>1. <!–[endif]–>Pure tone audiometric air conduction testing
presenting a pure tone to the ear through an earphone and measuring the lowest intensity in decibels (dB) at which this tone is perceived 50% of the time. This measurement is called threshold. The testing procedure is repeated at specific frequencies from 250 to 8000 hertz (Hz, or cycles per second) for each ear, and the thresholds are recorded on a graph called an audiogram. <!–[if !supportLineBreakNewLine]–> <!–[endif]–>

<!–[if !supportLists]–>2. <!–[endif]–>Bone-conduction testing
Done by gently resting bone-conductor on the mastoid process of the skull (the bone behind the ear) and is held in place by a small metal band stretching over the top of the head

3. Impedance audiometry

A hermetic seal is obtained by inserting a probe tip in the external ear canal. The pressure in the enclosed cavity is varied from + 200 to − 200 mm H₂O and the change in sound pressure level of a probe tone is graphed

4. Auditory brainstem response (ABR) audiometry

Electrodes are placed on the patient’s vertex, earlobes, and forehead. Clicks are delivered through earphones, and a computer sums the time-locked responses (potentials) for the first 10 msec after sound stimulation.

*Pure tone test – 1 & 2. Masking noise is sometimes used in the nontest ear to prevent its participation in the test

Hearing thresholds within normal ranges for the left ear

White area represents the sounds that the person would not hear (softer then their thresholds) and the tan area indicates all of the sounds that the person would be able to hear (louder then their thresholds).

Thresholds from zero to 15 dB are considered to be within the normal hearing range. After that point, people will usually begin to display some communication difficulties because of the elevated hearing thresholds. The 100 dB point should not be confused with a 100% hearing loss, which is a total lack of hearing.

 

 

http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=cm&part=A3897

http://www.hearingresearch.org/Dr.Ross/Audiogram/Audiogram.htm

http://www.audiologyawareness.com/hearinfo_audiogramread.asp

Changes may put therapists out of work

There is the fear that scores of aromatherapists, reflexologists and massage therapists will be put out of business if proposed changes to the registration of therapeutic health practitioners go ahead.

The Allied Health Professions Council of South Africa (AHPCSA) wants to petition the minister of health to change legislation so that the term “therapeutic” is removed from the names of the professions of aromatherapy, massage therapy and reflexology.

This means people in these fields would be known as practitioners. They would also have to register with the health council.

Tracy Chambers of the SA Association of Health and Skincare Professionals said this would influence the entire industry, as anyone wanting to practise reflexology or aromatherapy would have to comply with council regulations.

The council has said the reason for the change was to prevent people from practising as therapeutic therapists without registering with them.

Chambers said the distinction between therapeutic – meaning that it was used for healing – and non-therapeutic treatments was misleading, as both required the same knowledge.

Registered therapeutic practitioners would also be barred from offering treatment in any circumstances other than medical referrals.

“It impinges hugely on the industry,” Chambers said.

Gayl Hansen, director of the Cape Institute for Allied Health Studies, said the proposed changes did not look at the “bigger picture” of the need for basic skills at grassroots levels.

There is speculation that practitioners wanting to register with the AHPCSA would have to do a four-year degree – meaning they could practise on a clinical level.

“This is very short-sighted,” Hansen said.

She said the council needed to have multiple levels of entry and training in the health care industry so that therapists with basic training could still work in beauty salons.

Therapists with clinical training tended to work for themselves, not in a spa or beauty salon.

However, the non-registered therapist without clinical training, but with the skills to do reflexology or massage therapy, would be unable to practise.

Debbie Drake-Hoffmann, the registrar of the AHPCSA, said the change would not put therapists without clinical training out of business.

“On the contrary, if spas employed registered therapists it would ensure the public received standardised quality treatments.”

She said current legislation prevented council-registered practitioners from working for health spas or beauty salons, but the council was reviewing these regulations.

The deadline for comments on the AHPCSA’s proposed changes is July 31.

This article was originally published on page 3 of The Star on June 19, 2008

Wayne Rudmose and His Audiometry Equipment

Rudmose Associates Audiometers First Introduced in the 1960s

© Marie Brannon

Apr 23, 2009

 

Harvard-trained physicist Wayne Rudmose was a pioneer in the field of acoustics who developed instruments for measuring sound, including the first automatic audiometer.

 

A native Texan, Dr. Rudmose received his Ph.D. from Harvard in 1946 after obtaining his undergraduate degrees from the University of Texas and taking a break to serve in World War II. He became a professor of Physics at Southern Methodist University in Dallas and continued his research.

Rudmose Associates Develops Automated Stimulus Intensity Apparatus

While at SMU, Dr. Rudmose formed Rudmose Associates to produce and market his original designs. He introduced the first variable pulse depth audiometer, which added automated features to the manual units of the day. It was called the RA-101, and it allowed the subject to search for his own hearing threshold while the operator maintained complete control over the settings and frequency of trials. This instrument had earphones called Otocups which were individually compensated at each frequency. Several more versions of this testing device followed, including those for two-subject and four-subject group testing.

The Rudmose Model ARJ Recording Audiometers

The Rudmose Associates ARJ series was a commercially available apparatus, mostly used by groups such as schools. It was the next generation of audiometer technology and had automated intensity, frequency and data recording functions. A punchcard was placed in the unit and the subject was instructed to press a button on a hand switch to indicate whether a tone was audible. This equipment was first tested at the 1955 Wisconsin State Fair, in specially constructed booths. By the late 1960s employee-controlled self-recording audiometers determined the hearing level by tracing lines on a rectangular card proportional to the employee’s hearing thresholds. The audiometers could be grouped together for concurrent testing of multiple employees or other subjects.

Tracor, Inc. Acquires Rudmose Associates in 1963

When his company was acquired by Tracor, Inc. in 1963, Dr. Rudmose left S.M.U. and moved his family from Dallas to Austin, Texas. He continued with his inventions and developed other diagnostic instrumentation, including a device to detect hearing irregularities in newborns. He remained interested in acoustics and audiometrics for the rest of his life although he retired from Tracor in 1980 at the age of sixty-five.

Wayne Rudmose Also Designed Sound Systems

Dr. Rudmose was a tireless researcher who made significant contributions to his field by designing machines to test the hearing of newborns, children and adults. He also designed sound systems for many private and public buildings. Some of them are Love Field Airport in Dallas, the Coliseum at Southern Methodist University, and an airport in San Juan, Puerto Rico. He was the author of numerous academic papers and was active in the Acoustical Society of America. He died in 2006 in Austin, Texas.

 

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References:

Jerger, James (ed), Modern Developments in Audiology, New York: Academic Press 1963

Wayne Rudmose obituary 2006 , ancestry.com/topics.obits

 

The copyright of the article Wayne Rudmose and His Audiometry Equipment in Collectibles is owned by Marie Brannon. Permission to republish Wayne Rudmose and His Audiometry Equipment in print or online must be granted by the author in writing.

 

Rudmose Associates Model ARJ Recording Audiometer

Rudmose Associates Model RA101 with Otocups

Read more: “Wayne Rudmose and His Audiometry Equipment: Rudmose Associates Audiometers First Introduced in the 1960s” – http://collectibles.suite101.com/article.cfm/wayne_rudmose_and_his_audiometry_equipment#ixzz0DxfGukSg&A