his 240 - removing the ear plug effect

Removing the “Earplug” Effect

Central to the success of any hearing aid fitting is the process of controlling occlusion effects, acoustic or non-acoustic.

The most basic method of reducing or eliminating occlusion effects is by Venting.

However, opening an air channel through an acoustic coupling is not the only way of mitigating occlusion.


Occlusion is created when either supra-aural or insert earphones are placed on the patient during standard audiometry.

It is also present when ear impressions are in place.

Since these two conditions are nearly universal in hearing instrument fitting, the opportunity for evaluating occlusion effect is readily available.


Assessment of the degree of occlusion effect is a fundamental step in the fitting of any hearing instrument.

Occlusion is the perception of changes in auditory processing as a result of some type of blockage of sound transmission.


Such loss of transmission efficiency is already in place with a conductive or mixed hearing loss.

The presence of a significant (roughly 15 dB or greater) air-bone gap yields enough occlusion that further plugging by an acoustic coupler will generally have little effect.


Traditional venting charts have attempted to prescribe different size vents based on degrees of hearing loss.

General comments such as "persons with more than 60 dB of loss will not experience occlusion", should be disregarded in that experience has shown occlusion effects to be present even in the most profound losses.


Incidents of central auditory processing disorders, such as those found in post-stroke, dementia, head trauma, and the growing variety of survivable pathologies, produce cases which require special care.


The general process of utilizing larger vents with milder losses is of considerable value.

Any rules of venting can be expected to be modified by changes in the way in which the brain handles sound.


The degree of bone conduction (BC) sound enhancement in the presence of occlusion varies considerably with different occluding object types.

The degree of (BC) threshold improvement under occlusion should also be expected to vary considerably from individual to individual.


Testing BC while the patient is occluded addresses the "hollow voice" aspects of occlusion. Three tests may be used in this process. They are: 1. Weber testing, to include lateralization

measurements from 25OHz- 4000Hz. 2. (BC) thresholds at 1 kHz, 750 Hz, 500 Hz,

and 250 Hz; measured at each ear’s mastoid process.

3. (BC) SRTs may also be measured for each ear.


Comparison of occluded (absolute) BC with non-occluded (relative) BC results indicates the amount of BC sound enhancement caused by occlusion.

True comparison requires each of these tests be administered while the patient is both occluded and non-occluded.


This described test regimen will provide significant information regarding occlusion.

Note: The assessment of the lateralization of (BC) frequencies, indicates important information regarding potential binaural vs. monaural occlusion problems.


The revealed improvement of low frequency thresholds under occlusion is a good indicator of how the client will react to the sound of their own voice while wearing hearing instruments.

Also, the revealed differences between (BC) SRTs under occlusion modify the Stenger effect.


An alternate test procedure used to measure the output of a person's own voice, in situations, while occluded, involves the use of a probe microphone.

Many speech components are measurable using this measurement method.


Three simple vowel sounds are recommended due to their spectral content. From highest to lowest frequency, they are /i/ (as in eat); /a/ (as in ah); and /u/ (as in boot).

Probe microphone measures, using these simple vowel sounds, can provide a valuable “comparison tool” when evaluating the effect of vents or object/material changes.


Since a vent is usually a separate air cavity in a hearing instrument fitting, its’ individual resonant and impedance characteristics may be expected to change when constructed of different (soft or hard) materials.


The size and shape of the ear canal limits the amount of room available for building a vent.

The canal direction and shape must be considered as a part of placing/constructing a vent.

Otoscopic examination, looking through the vent, can often reveal whether it is open into the canal, striking the canal wall, etc.


The fit of the coupling in the ear dictates the presence of leakage around the shell or ear mold of the instrument. Contact between the earpiece and the ear itself, as well as retention changes due to mandibular movement, each play a crucial part in the degree of potential occlusion involved in a hearing instrument fitting. Please Note: The presence of slit leaks may have a positive or negative effect upon the occlusion performance of an individual.


Standard vents are found in three traditional configurations. They are:1. External vents 2. parallel vents 3. diagonal vents Note: External and parallel vents operate on the same principle, with the only real difference being the use of plastic versus human ear canal walls to achieve the vent space.


External VentingThe external vent remains highly

useful in cases of drainage and relief of non-acoustic occlusion effects.

External vents probably provide the greatest potential for relief of feelings of pressure in the ear.


Parallel Venting Parallel vents remain the most

popular vent configuration, since they provide potential low frequency sound reduction with minimal high frequency loss, and lower incidence of electro-acoustic feedback.

The parallel vent provides greater ease of retention of the aid than is generally found with the external vent.


Diagonal Venting The diagonal vent, which opens directly

into the sound bore, has been found to have a higher incidence of feedback. In addition, it causes reduction of the high frequency output.

While not commonly used in ITE or ITC fittings, the occurrence of a narrow canal tip with a belled end, in which the vent and sound bore emerge in very close proximity, can create the same effect as an actual diagonal vent.


Important Venting “tips” To Remember

VENT ALWAYS: Occlusion should be addressed in every fitting—remember, ears need to “breathe”. In the age of high cut filters, notch filters, phase shifting, and digital control, the fear of feedback can be reduced along with feedback itself.



Given the array of electronic and plastic technologies available today, there remains little reason for unvented fittings, unless the client expresses desire for such an arrangement.

Closing off the vent is actually a good first step in acoustic modification.

It is rare, but some clients prefer no venting.



A VENT IS ONLY AS LARGE AS ITS' NARROWEST OPENING: This is the guiding principle behind select-a-vent and positive variable vent systems. A change in the diameter at one point in a vent yields changes in the overall function of the entire vent.



VENTING TO ADD LOWS? Like every other physical object, a vent will have a resonant frequency. While its general impedance is minimal for low frequencies, a vent between 1 and 3 mm in diameter can cause resonant increases in low frequency amplification.



The exact nature of such a low frequency boost depends on a number of factors; but may generally be summarized as follows: the smaller the vent, the lower the resonant frequency boost.


Considerations for Deep Insertion Fittings

Finally, in relation to occlusion effects, the placement of a damping object in contact within the bony meatus has the potential to alter the temporal location of internal bone conducted sounds.



There are a number of concerns associated with such fittings. The bony meatus is a highly sensitive area, composed of extremely thin skin over bone.



This area is filled with multiple neural plexi.

The sensitivity of this region could (and does) cause discomfort in wearing a deeply seated hearing instrument.

This situation is potentially aggravated by movement from the temporal-mandibular joint.

his 240 - removing the ear plug effect

Health & Medicine

occlusion effectis

degreeof potential occlusion

way ofmitigating occlusion

bc thresholds

monaural occlusion problems

testing bc

occlusion effects tobe

bc srts