**2.2 Objective evaluation (technology)**

Diagnostic equipment can help to identify different degrees of hearing loss in a more quantitative fashion. There are several techniques that are implemented in medical equipment for screening of hearing. The most widely used initial screen involves a puretone, air-conduction hearing test or audiometry, followed by tympanometry, otoacoustic emissions, multilingual speech audiometry, and stem cell evoked potentials.

Hearing testing is conducted in the audiometry testing chamber; a special sound booth is built into this room, which must be constructed based on testing guidance described in the ASTM E336 "Standard Test Method for measurement of Airborne Sound Insulation in Buildings" (ASTM E336–10, 2011). This triangular-shaped booth is designed to ensure that the sound levels inside are sufficiently quiet to permit accurate hearing-threshold measurements. In addition to the sound booth, the examination room possesses several other features designed to reduce sound levels in the room further, as shown in Figure 3. These include sound dampening materials on the interior walls of the examination room and a rubber seal on the exterior door.

Fig. 3. Anaechoic Chamber for audiometry test.

Technology for Hearing Evaluation 9

Generally, an audiometric system controlled by a microprocessor (Penhaker & Kijonka, 2011) is composed of two channels: one for test ear stimulus, and other as a non-test ear

Fig. 5. A patient's Békésy test (Gutierrez et al., 2009)

masker, as shown in the block diagram of Figure 6.

Fig. 6. General block diagram of an audiometer

The testing suite consists of two adjoining rooms: one of single-wall construction, and the other, of double-wall construction. The double portion of the suite is the subject of the noise reduction test that includes the following: 1) generating a high-volume controlled sound field outside the testing chamber; 2) measuring the sound pressure level at the outer wall; 3) measuring the attenuated sound-pressure level of the controlled sound field inside the test chamber, and 4) subtracting internal from the external sound-pressure levels while making corrections for the interior ambient sound pressure level (Acoustic Systems MD, 2000).

#### **2.2.1 Pure-tone audiometry and logoaudiometry**

The Audiometry study is used to diagnose the degree and type of hearing loss by determining the faintest tones that a person can hear at selected pitches; the measuring equipment utilized is called audiometer. This device emits a pure tone by means of a fixedfrequency oscillator calibrated at the decibel hearing level (National Health and Nutrition Examination Survey, 2003); frequencies (125-8000 Hz) and intensities (0-110 dB) which can be varied. This unit is controlled by a microprocessor that is sometimes available as a handheld Windows-driven instrument and possesses high accuracy and efficiency (Khandpur, 2005). Such systems can be also employed with bone vibrators to test conductive hearing mechanisms. A pair of headphones is attached, and a test subject feedback button indicates when the subject has heard the sound. On the one hand, audiometry measures hearing thresholds and oral audiometry or logoaudiometry (Aguilera et al., 1997), considered to be a subjective evaluation, is defined by the capacity to evaluate the human speech understanding consists of supplying the patient with words at different energies that aid in recognizing acoustical features and in providing clues concerning the etiology of the hearing loss. On the other hand, audiometry includes supraliminal tests such as SISI*,* Fowler, Tone Decay, or Békésy, to suggest the sensorineural damage (Ghani, 2005). Figures 4 and 5 ilustrate the SISI and Békésy tests.

Fig. 4. A patient's SISI Graph with score value (Gutierrez et al., 2009)

The testing suite consists of two adjoining rooms: one of single-wall construction, and the other, of double-wall construction. The double portion of the suite is the subject of the noise reduction test that includes the following: 1) generating a high-volume controlled sound field outside the testing chamber; 2) measuring the sound pressure level at the outer wall; 3) measuring the attenuated sound-pressure level of the controlled sound field inside the test chamber, and 4) subtracting internal from the external sound-pressure levels while making corrections for the interior ambient sound pressure level (Acoustic Systems MD, 2000).

The Audiometry study is used to diagnose the degree and type of hearing loss by determining the faintest tones that a person can hear at selected pitches; the measuring equipment utilized is called audiometer. This device emits a pure tone by means of a fixedfrequency oscillator calibrated at the decibel hearing level (National Health and Nutrition Examination Survey, 2003); frequencies (125-8000 Hz) and intensities (0-110 dB) which can be varied. This unit is controlled by a microprocessor that is sometimes available as a handheld Windows-driven instrument and possesses high accuracy and efficiency (Khandpur, 2005). Such systems can be also employed with bone vibrators to test conductive hearing mechanisms. A pair of headphones is attached, and a test subject feedback button indicates when the subject has heard the sound. On the one hand, audiometry measures hearing thresholds and oral audiometry or logoaudiometry (Aguilera et al., 1997), considered to be a subjective evaluation, is defined by the capacity to evaluate the human speech understanding consists of supplying the patient with words at different energies that aid in recognizing acoustical features and in providing clues concerning the etiology of the hearing loss. On the other hand, audiometry includes supraliminal tests such as SISI*,* Fowler, Tone Decay, or Békésy, to suggest the sensorineural damage (Ghani, 2005).

**2.2.1 Pure-tone audiometry and logoaudiometry** 

Figures 4 and 5 ilustrate the SISI and Békésy tests.

Fig. 4. A patient's SISI Graph with score value (Gutierrez et al., 2009)

Fig. 5. A patient's Békésy test (Gutierrez et al., 2009)

Generally, an audiometric system controlled by a microprocessor (Penhaker & Kijonka, 2011) is composed of two channels: one for test ear stimulus, and other as a non-test ear masker, as shown in the block diagram of Figure 6.

Fig. 6. General block diagram of an audiometer

Technology for Hearing Evaluation 11

when new patient data is introduced, the information of the previous test is lost. There is no database and the hardcopy audiograms are not designed for long term storage because the

This limitation is a problem for the specialist, because he/she needs to store the patient's test data so that this information can be used in clinical and research audiometric protocols. Some authors (Gutiérrez et al., 2009) have described the design and implementation of a communication and graphical module for transmitting, processing, printing, and storing the patient's special audiometric studies as a substitute for the NOAH-3™ System (see Figure 7).

The Impedance Audiometry or most commonly used Tympanometry, is a magnitude that examines the condition of the middle ear, the status and mobility of the eardrum (tympanic membrane). The equipment produces variations of air pressure in the ear canal by means of a probe measuring the middle ear's acoustic resistance. The secondary purpose of this examination is to evaluate the acoustic reflex pathway which includes the 7th and 8th cranial nerves and the brain stem. Furthermore, tympanometry permits a distinction between sensorineural and conductive hearing loss when results are not apparent via Weber and Rinne testing. It is also helpful in the diagnosis of otitis media by demonstrating the presence of middle-ear effusion. When sound impacts on the eardrum, part of the sound is absorbed and sent via the middle to the inner ear, while the remaining part of the sound is reflected. When the eardrum is inflamed over a long period of time, it can become stiff and heavy and the majority of the sound is reflected; therefore less sound reach the inner ear. Among other things, tympanometery assesses cochlear integrity and evaluates acoustic impedance, i.e., the degree of difficulty that the middle ear and ossicles encounter for the passage of sounds, as a result of the mass, stiffness and ossicular disruption of the auditory system. If there is fluid behind the ear-drum, it will not move back and forth from its resting position when pressure is applied. Tympanometry is thus affected by the mass, mobility,

The instrument, or tympanometer, applies air pressure to the eardrum and measures the reflected sound. Inside the instrument's probe, a small loudspeaker is installed that emits a tone, typically at 226 Hz, through a tube into the auditory canal in front of the eardrum. The canal's air pressure is altered between +200 and -400 decapascals (dapa), at which the sound strikes the tympanic membrane, causing middle-ear vibration, which in turn results in the perception of hearing. Some of this sound is reflected back and picked up by another tube, which is connected to the microphone inside the probe that receives the sound. Together with a third tube, all three are inserted nearly into the eardrum and are made airtight against outside pressure by the ear tip. A manometer and a pump, which can produce both positive and negative pressure, are connected to tube **C**. Less sound is reflected into the microphone when the eardrum is stiff and the eardrum transmits the majority of the sound via the middle to the inner ear. Highest compliance is normally reached with air pressure that corresponds to the outside pressure. During tympanometric measurement, a continuous change in positive and negative pressure is produced by the instrument's pump in the outer middle auditory canal. This test should not be performed in infants below 7 months of age because the suppleness of the external canal's cartilage may produce

and resistance systems of the external and middle-ear cavities.

audiometer has a thermal printer.

**2.2.2 Tympanometry** 

misleading results.

An audiogram is a chart that depicts the results of the audiometric study; on the x-axis, frequencies are represented in Hz, and on the y-axis, the patient's hearing ability is expressed in dB. Two charts are usually employed: one for the right ear, and one for the left. The right ear is graphed with a circle in red color, the blue color plot the left ear with an X. Symbols and notes should correspond to the recommendations and standards of the American Speech Language Hearing Association (ASHA).

ASHA guidelines for manual pure-tone threshold audiometry *(*Campbell et al., 2010*);* these guidelines contain procedures for performing a hearing diagnosis and for monitoring standard pure-tone threshold and include manual air-conduction and bone-conduction, masking. From the inception of modern audiometric technology, staff at the Department of Audiology at the Massachusetts Eye and Ear Infirmary began using an extension of the standard symbols for designating "response at limit" and responses found using speakers (Halpin, 2007). These symbols represent new exploratory developments and are not part of the ASHA standard symbol.

The NOAH-3™ System (Hearing Instrument Manufacturers' Software Association, 2000) is a database that integrates software applications from the several manufacturers of audiologic devices, including Madsen™ (Madsen Electronics*,* 2004), Amplaid™, Interacustic™, Benson Medical™ . The main purpose of NOAH is to control data exchange from an audiometer to a personal computer, among other applications. The transmitted information is introduced into a database that is manipulated and processed to obtain audiograms, tables, measurements, and statistics, as well as to save and print the patient's study.

Fig. 7. Overview Producer-Consumer Architecture for the Audiometer Interface.

The NOAH-3™ System does not work with certain special tests (SISI, Békésy) and some audiometers, for example, Madsen™ (Gutiérrez et al., 2009), and it is not possible to transfer data for processing or printing these special tests. When the audiometer is turned off, or

An audiogram is a chart that depicts the results of the audiometric study; on the x-axis, frequencies are represented in Hz, and on the y-axis, the patient's hearing ability is expressed in dB. Two charts are usually employed: one for the right ear, and one for the left. The right ear is graphed with a circle in red color, the blue color plot the left ear with an X. Symbols and notes should correspond to the recommendations and standards of the

ASHA guidelines for manual pure-tone threshold audiometry *(*Campbell et al., 2010*);* these guidelines contain procedures for performing a hearing diagnosis and for monitoring standard pure-tone threshold and include manual air-conduction and bone-conduction, masking. From the inception of modern audiometric technology, staff at the Department of Audiology at the Massachusetts Eye and Ear Infirmary began using an extension of the standard symbols for designating "response at limit" and responses found using speakers (Halpin, 2007). These symbols represent new exploratory developments and are not part of

The NOAH-3™ System (Hearing Instrument Manufacturers' Software Association, 2000) is a database that integrates software applications from the several manufacturers of audiologic devices, including Madsen™ (Madsen Electronics*,* 2004), Amplaid™, Interacustic™, Benson Medical™ . The main purpose of NOAH is to control data exchange from an audiometer to a personal computer, among other applications. The transmitted information is introduced into a database that is manipulated and processed to obtain audiograms, tables, measurements,

Fig. 7. Overview Producer-Consumer Architecture for the Audiometer Interface.

The NOAH-3™ System does not work with certain special tests (SISI, Békésy) and some audiometers, for example, Madsen™ (Gutiérrez et al., 2009), and it is not possible to transfer data for processing or printing these special tests. When the audiometer is turned off, or

American Speech Language Hearing Association (ASHA).

and statistics, as well as to save and print the patient's study.

the ASHA standard symbol.

when new patient data is introduced, the information of the previous test is lost. There is no database and the hardcopy audiograms are not designed for long term storage because the audiometer has a thermal printer.

This limitation is a problem for the specialist, because he/she needs to store the patient's test data so that this information can be used in clinical and research audiometric protocols. Some authors (Gutiérrez et al., 2009) have described the design and implementation of a communication and graphical module for transmitting, processing, printing, and storing the patient's special audiometric studies as a substitute for the NOAH-3™ System (see Figure 7).
