Tag Archives: OAE

Music from the ear: Researchers show how an objective audiometric test can become even more reliable

Music from the ear: Researchers show how an objective audiometric test can become even more reliable.

Physikalisch-Technische Bundesanstalt (PTB). ,ScienceDaily, 10 Jan. 2013. Web. 11 Jan. 2013. 

Not only can the human ear detect sounds, it can also generate them. If the ear hears the two upper tones of a major triad, it produces the fundamental of the chord which can then be measured. This phenomenon, called “otoacoustic emission” (OAE), is used by otologists for objective audiometric tests, e.g. in newborns. Investigations at the Physikalisch-Technische Bundesanstalt (PTB) have shown that an OAE audiometric test becomes even more reliable if the two sounds are transmitted to the ear not via a loudspeaker, but by bone conduction.

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image from PTB

Combined stimulation of otoacoustic emissions: the first tone is transmitted via air conduction (probe speaker in the ear), the second tone is conveyed via bone conduction (bone vibrator behind the ear).

Regardless of where people come from, whether they are Europeans or Asians, the human ear is always tuned to a major scale. If the ear hears the two upper tones of a major triad, the ear itself produces the third, lowest, tone of the chord. This tone is called “distortion product otoacoustic emission (OAE)” and is generated due to anatomic and physical laws:

if the hair cells in the inner ear are healthy and sound, they are stimulated by the two matching tones to vibrate at a third frequency. This lower tone comes out of the ear again and can be measured by means of a highly sensitive microphone. With the aid of this phenomenon, it is possible to check objectively whether the hearing of newborns or infants is intact.

Such a test used to be performed using two tiny loudspeakers, each of which emitted a tone into the ear, as well as a miniaturized microphone, which recorded the third tone (if it came out at all).

If this tone is not generated, physicians have a first inkling that the baby might need therapy or a hearing aid.

However, it may be that the ear is healthy but does not “hum”. This can be caused by a badly calibrated loudspeaker, or due to the fact that the loudspeakers which are placed close to each other emit standing waves into the auditory canal which weaken one of the two tones.

To preclude such malfunctions, alternative tone generation methods have been investigated at PTB within the scope of a DFG project: so-called “bone vibrators” which, in analogy to a tuning fork set onto the bone, convey the tone directly to the bone located behind the ear.

The results have shown that both with two bone vibrators and in combination with a loudspeaker, correct otoacoustic emissions are generated. This not only allowed calibration errors to be reduced, but also provided physicians with improved differential diagnosis possibilities, since with the new procedure, they can test the function of the inner ear without a doubt and, potential damage of the middle ear, thus, has less influence. Clinical studies should follow.

Scientific publication

Zebian, M.: Calibration of Distortion Product Otoacoustic Emission Probes. Dissertation, TU Braunschweig (2012)

Hearing Screening in Newborn

When Mishi (name changed) was born her parents were extra cautious for her hearing as her elder sister now 4 years old has cochlear implantation done.

They visited audiologist for hearing evaluation. Their worst fears was confirmed, Mishi now 6 months has severe to profound hearing loss and is fitted with hearing aids. But there is hope, as she is young she will most probably lead normal life like her elder sister which was intervened early and appropriately.

On the other hand khushi is 3 and ½ years old, pediatrician immediately referred her to audiologist for delayed speech, thanks to increasing awareness in Navi Mumbai. But even after confirmation of hearing loss, they are not willing for intervention as her father thinks she will start talking with time.

 

Importance of assessing hearing in a new-born child:

Two out of every 100 children under 6 years of age have permanent moderate deafness and 1-4 out of every 1,000 newborns have significant hearing loss.

Birth to 3 years are critical for speech and language development and if child does not hear the sound, he can not speak, even a mild or one sided hearing loss can affect speech language skills, academic & intellectual skills, and it affects individual for the rest of his life.

“American Academy of Pediatrics recommends new born hearing screening and periodic hearing testing for first three years of life. Joint Committee on Infant Hearing (JCIH, 1994) recommends that all infants with hearing loss should be identified by 3 months of age, and should be fitted with hearing aids or cochlear implant and receive services to help them learn to listen and speak by 6 months of age.

 

Importance of OAE hearing screening:

Newborns, infants and children below 5 years are difficult to diagnose by routine tests. Traditional subjective methods of behavioral observation to ringing bells and hand clapping are not fully reliable as child may respond to some sound because of residual hearing or they may take cues from visual prompts, at the same time child with normal hearing may not respond.

Prior to Objective tests such as OAE, infants with hearing loss typically remained unidentified until 2 ½ years of age. – far too late for optimal language development.

Advances in technology make it possible to assess the hearing of infants even while they are asleep.

 

Method for hearing screening Otoacoustic Emission (OAE):  

A small probe is placed in the child’s ear canal. This probe delivers a low-volume sound stimulus into the ear, which travels from middle ear to inner ear. If hearing is good this sound will bounce back as echo generated by outer hair cells of cochlea (called OAE)  and is measured with a microphone.

In approximately 30 seconds, the result is displayed on the screening unit as a “pass” or “refer.”

It is very important to remember that fail OAE  does not mean child have haring loss it just indicates that further  tests are required for full hearing evaluation. (BERA and ASSR test).

 

Newborn hearing screening in India:

 In developed countries like US it is mandatory to check hearing of each and every newborn within 48 hours of birth. But currently there are no mandatory rules or regulations for Newborn Hearing Screening in India and hence the identification of hearing loss is mostly at later ages.

 

Conclusion:

OAE screening is proved to be reliable method of screening. If hearing screening is made mandatory for the newborns at the time of birth or within the first month of life many more cases of hearing & speech impairment could be avoided.

Hearing impairment must be corrected before the child reaches six months of age. Late intervention of the hearing loss will yield very poor results as the plasticity of the brain reduces drastically as the child grows older. Undetected hearing loss is big obstacle to educational achievement and socialization.

Mother’s instinct should never be ignored and probable hearing loss in the child should be subjected to audio logical assessment.  It should not be ignored withIt shall improve in the next few years” or ‘child did not hear because he was busy playing or watching television’.

For more information about OAE screening visit hearing screening protocol at Audicco

or mail at info@audicco.com

Newborn Hearing Screening

  • Why Newborn Hearing  Screening?

  • How early should I have my baby’s hearing screened?

  • How is Hearing screening in newborn done?

  • What are the advantages of OAE screening?

  • What does ‘REFER’ or ‘FAIL’ mean?

  • What is the Hearing Screening Protocol at Audicco Gliriaa?

  • What are some of the warning signs of hearing loss in an infant?

Why Newborn Hearing  Screening?

Newborn babies learn to recognize the familiar sounds in their home in their first few months of life.  Baby if can’t hear the sound, can’t speak, profound hearing loss can lead to dumbness.  Even partial Hearing loss in children can impair normal development of speech & language, his emotional balance, academic & intellectual skills and it affects individual for the rest of his life.

Subjective methods, such as ringing bells and hand clapping have not proven to be reliable for screening. Prior to Objective hearing tests such as OAE, infants with hearing loss typically remained unidentified until 2 ½ years of age. – far too late for optimal language development.

How early should I have my baby’s hearing screened?

  Your baby should have a hearing screening at birth or within the first month of life. If hearing loss is confirmed, it’s important to consider the use of hearing Aids or Cochlear Implant by 6 months of age. Hearing should be tested as child grows at any time on slightest suspicion of hearing deficit by Parents, care givers, teachers and family doctors.

How is Hearing screening in newborn done?

The procedure is performed with a portable hand held screening unit.

OAE screening–A small probe is placed in the child’s ear canal. This probe delivers a low-volume sound stimulus into the ear.

Tone or click stimuli are delivered, which travels from middle ear to inner ear where OAE is generated by the outer hair cells of the cochlea. This travels back and is measured with a microphone.

In approximately 30 seconds, the result is displayed on the screening unit as a “pass” or “refer.”

 

Automated ABR screening – Disposable surface electrodes are placed high on the forehead, on the mastoid, and on the nape of the neck.

The click stimulus (usually set at 35 dB hearing level [HL]) is delivered to the infant’s ear via small disposable earphones designed to attenuate background noise.

As with OAE screening, the sound travels through the outer, middle, and inner ear. However, in ABR, the sound continues along the eighth nerve to the brain.

An electrical response from that nerve is picked up by electrodes strategically placed on the infant’s head. This response is recorded and analyzed.

However, it lacks frequency-specific information and requires increased preparation time prior to testing.

What are the advantages of OAE screening?

Handheld otoacoustic emissions (OAE) screening is the most practical method for screening infants and toddlers because it :

  • objective and not dependent on a behavioral response from the child
  • Reliable and efficient
  • Help to detect sensorineural hearing loss and wide range of hearing-health concerns.
  • Is quick and painless
  • Simple and portable

 

What does ‘REFER’ or ‘FAIL’ mean?

 

Refer, an absent response to a click, does not always mean total deafness, but it does mean that your baby needs his/her hearing looking at more carefully.

The ear will not pass the screening if there is –

(a)  Blockage in the ear canal by wax or  amniotic,

(b) Structural problem or excess fluid in the middle ear

(c) Impaired cochlea that is not responding normally to sound.

What is the Hearing Screening Protocol ?

 All newborn should be screened at birth, or, within a month’s time.

 

Visual inspection – Outer ear abnormalities, foreign objects or blockage in the ear canal, any fluids draining from the ear, or noticeable odor; if any abnormal conditions are present, medical management should be done by ENT specialist.

 

Ist OAE screening – If both Ears Pass the test, the child’s hearing screening is considered complete

Those who have high-risk for hearing loss should be followed up at intervals of 6 months even if they are cleared at the screening. (As per Joint Committee on Infant Hearing 2000 position statement)

If the child does not pass the screening on any ear child is evaluated and managed by ENT specialist for a possible middle ear disorder within 3 months of age.

Repeat OAE screeningAfter treatment and/or medical clearance is obtained, the OAE screening is repeated.

If the ear passes the test, no further screening

However, if the ear dues not pass the Repeat test child is referred to a pediatric audiologist for complete Hearing evaluation like BERA (ABR), ASSR and Impedance.

Appropriate measures such as hearing aid fitting initiated before 6 months.

 

What are some of the warning signs of hearing loss in an infant?


If your child does not startle to loud noises or awaken from sleep by very loud noises in the house.

If your child is not babbling repetitively (ba ba, da da, etc.) by 8-10 months or

if your child doesn’t turn to localize the source of your voice by 7-8 months, you should be suspicious.

Ask for an objective set of tests.