Average hearing threshold at 500, 1000 and 2000 Hz is called Fletcher index.
Q. WHAT IS SPEECH RECEPTION THRESHOLD?
Speech reception threshold (SRT) is the minimum intensity level in dB at which 50% of the spondee (two syllable words such as black night, foot ball, day dream, sunlight ) words can be repeated correctly.
Generally SRT is ±10 dB of the average of 3 speech frequencies.
Q. WHAT IS SPEECH DISCRIMINATION SCORE?
Speech discrimination score or optimum discrimination score is the maximum percentage of the correct score when phonetically balanced (single syllable words e.g. pin, sin, bus, fun, run ) are used.
In normal or CHL: SDS is 95-100%
In cochlear lesion: SDS is decreased
In retrocochear lesion: SDS is very poor and ” ROLL OVER OHENOMENON” is present ( As the intensity increases the score decreases)
SDS <80 % affect the ability to understand speech. It helps to find out whether or not the hearing aids will be beneficial.
Q. WHAT ARE THE ADVANTAGES OF PURETONE AUDIOMETRY?
It also helps to diagnose specific diseases such as
It serves as the record for the legal purpose and future reference.
It can also be the basis for prescribing hearing aid.
It helps to find out the speech reception threshold.
Q. WHAT ARE THE ADVANTAGES OF SPEECH AUDIOMETRY?
It helps to differentiate organic and functional hearing loss.
It helps to differentiateCochlear and Retrocochlear hearing loss.
It helps to fit appropriate hearing aid.
Q. WHAT ARE THE DIFFERENT PATTERN OF AUDIOGRAMS FOUND IN VARIOUS CONDITION LEADING TO CHL?
TYPE OF AUDIOGRAM
Left sloping (Loss in lower frequencies)
Right sloping (Loss in higher frequencies)
Ossicular chain disruption
A large Air- Bone gap
-Bone conduction dip at 2 KHz (Carhart's notch)
Q.WHAT ARE THE DIFFERENT PATTERN OF AUDIOGRAMS FOUND IN VARIOUS CONDITION LEADING TO SNHL?
TYPE OF AUDIOGRAM
Trough shape or Dish pattern
Sudden dip at 4000 Hz both in AC and BC
Greater levels of hearing loss in higher frequency
Q. WHAT ARE THE AUDIOMETRIC FINDINGS IN MIXED DEAFNESS?
Both BC and AC drop
Air-Bone gap still present
BC > 20dB
AB gap > 15 dB
Q.WHAT ARE THE VARIOUS TYPES OF GRAPHS RECORDED IN BEKESY’S AUDIOMETRY?
TWO TRACING NEVER OVERLAP
Both C & I tracing overlap
C & I tracing overlap up to 1000 Hz after which the C tracing drops down by 15-20 dB
C tracing drops down by > 20 dB
C tracing are weak
Two tracings are widely separated and C tracing better than I tracing
Q. WHAT IS RECRUITMENT? WHAT ARE THE DIFFERENT TYPES OF TESTS FOR THE RECRUITMENT?
Recruitment is an abnormally rapid increase in loudness with increasing sound intensity where an ear which doesn’t hear the low intensity sound will hear the greater intensity sounds as loud or even louder than the normal ear.
Recruitment is seen in cochlear type of SNHL:
The following are the various tests that are used for recruitment: