The purpose of the audiologic assessment is to
- assess the integrity of the auditory system in each ear,
- measure hearing sensitivities across frequencies,
- determine the type of hearing loss,
- establish a baseline for future monitoring,
- provide ear-specific information needed to initiate amplification device fitting,
- assess the impact of the degree of hearing loss on functionality and/or quality of life.
Audiologic assessment typically includes
- case history;
- acoustic immittance procedures, including tympanometry, static immittance, and acoustic reflex measures;
- otoacoustic emissions (OAEs) screening;
- pure tone audiometry-
- air conduction,
- bone conduction;
- speech audiometry-
- speech reception thresholds or speech detection/awareness thresholds,
- word recognition measures.
Additional tests may include
- self-assessments, including communication inventories and needs assessment inventories,
- auditory brainstem response (ABR).
Accurate diagnosis of hearing loss relies on the audiologist's interpretation of a test battery within the context of the individual's medical and/or developmental history. Case history information may indicate a need for modification of evaluation procedures. For example, the audiologist may include evaluation of the high-frequency region of the cochlea (above 4000 Hz) for an individual with a history of ototoxic drug exposure. Modification of routine assessment procedures also may be necessary to adequately evaluate individuals with multiple disabilities.
Examples of questions that might typically be included on a case history are listed below. The specific questions may vary, based on the age and circumstances of the patient.
Case history typically includes information related to
- family history of hearing loss;
- medical history, including
- general health history;
- history of ear infections;
- medication use (prescriptions and/or over-the-counter medications);
- presence of other disabilities;
- previous hearing screening and testing results;
- presence of pain or discharge from ears;
- history of dizziness, balance problems, or falls;
- presence of tinnitus;
- speech and language development;
- noise exposure, including during recreational and occupational activities;
- changes in social interaction;
- changes in academic performance;
- experience with social/emotional bullying;
- hearing history, including
- when the difficulty with hearing was first noticed;
- whether the onset of hearing loss was gradual or sudden;
- types of difficulties experienced (i.e., more difficulty hearing women's, men's, or children's voices; having to frequently ask people to repeat; hearing people speak, but not understanding what is being said);
- whether there are situations where it is more difficult to follow a conversation, such as a noisy restaurant, a theater, large groups, cars, etc.;
- feedback from others (e.g., comments regarding speaking too loudly in conversations or turning up the volume on the television).
Case history is recorded using a standard format. See the cultural competence Practice Portal page for information regarding
gathering a case history.
Visual inspection of the pinna and ear canal, including otoscopy, precedes audiometric testing to rule out active pathological conditions and the potential for ear canal collapse caused by audiometric earphones. The audiologist ensures that the external auditory canal is free of excessive cerumen before testing.
Acoustic immittance testing is useful in localizing the site of lesion for the hearing loss. Acoustic immittance testing may include tympanometry and/or acoustic reflex testing.
Tympanometry is performed with a 226 Hz probe signal. Parameters of tympanograms to be investigated include
- tympanometric peak pressure,
- tympanometric width,
- static immittance,
- ear canal volume,
- tympanometric shape.
A tympanogram is a graphic representation of the relationship of acoustic impedance and air pressure of the middle ear and the mobility of the tympanic membrane. Various middle ear pathologies (otitis media, otosclerosis, and tympanic membrane perforations) yield distinctive tympanograms. Compliance is plotted vertically on the tympanogram and is measured in ml or mmho. Maximum compliance of the middle ear system occurs when the pressure in the middle ear cavity is equal to the pressure in the external auditory canal. The maximum compliance value (static acoustic admittance) occurs at the highest peak of the curve on the graph (Figure 1). Pressure is indicated on the horizontal axis of the graph and is measured in decapascals.
Figure 1. Tympanogram Showing Maximum Peak Compliance
There are three main types of tympanograms: A, B, and C. In a Type A tympanogram, peak compliance occurs at or near atmospheric pressure, indicating a normal middle ear system, free of fluid or physiological anomalies that would prevent the admittance of sound from the middle ear into the cochlea. Figure 1 shows an example of a Type A tympanogram.
Type B tympanograms have no sharp peak and little or no variation in impedance over a wide sweep range. A Type B tympanogram (Figure 2) is indicative of middle ear pathology, such as fluid or infection behind the tympanic membrane. In some cases, these tympanograms are seen when there is a hole in the tympanic membrane with the difference being the ear canal volume: a larger ear canal volume indicates a perforation in the tympanic membrane.
Figure 2. Type B Tympanogram
Type C tympanograms (Figure 3) are similar in shape to Type A tympanograms, but are shifted negatively on the graph, with peak compliance significantly below zero (usually less than -200), indicating negative pressure within the middle ear space. This finding is often consistent with sinus or allergy congestion or the end-stages of a cold or otitis media.
Figure 3. Type C Tympanogram
Ipsilateral and contralateral acoustic reflexes are performed to assess the integrity of the acoustic reflex pathway. Acoustic reflex thresholds (ARTs) are measured at 500, 1000, and 2000 Hz. Testing at 4000 Hz is not recommended, because many people with normal hearing have elevated reflexes at this frequency (Gelfand, 1984; Silman & Silverman, 1991).
Normal ARTs range from about 85 to 100 dB SPL for pure tone stimuli (Gelfand, 1984).
- Conductive pathology: acoustic reflexes are
- typically absent in the probe ear, because the pathology prevents the ability to monitor changes in immittance at the probe tip, or
- typically elevated in the stimulus ear, because the stimulus reaching the cochlea is reduced by the amount of the air-bone gap.
- Sensorineural pathology: ARTs are dependent on hearing sensitivity.
- Retrocochlear pathology: pathology is associated with ARTs that are either elevated above what they would have been in sensorineural hearing loss (above the 90th percentile) or absent.
Acoustic reflex decay is the reduction in the magnitude of the acoustic reflex during a prolonged stimulus. Reflex decay is measured at 500 and 1000 Hz only, because rapid adaptation is common at higher stimulus frequencies. Reflex decay is typically measured contralaterally. Reflex decay is abnormal if the reflex is reduced more than 50% over the first 10 seconds. Abnormal reflex decay is associated with retrocochlear pathologies.
Otoacoustic emissions (OAEs) are used to assess cochlear function and are useful in differential diagnosis. OAEs are best measured in a quiet environment (e.g., in a quiet room with no one speaking and minimal background noise). A snug probe fit is essential for valid and reliable recordings. Ears are tested one at a time. Acceptable OAE protocols include
- Transient Evoked Otoacoustic Emission (TEOAE): One level (e.g., 80 dB pSPL) click stimulus. Normal distributions for this condition for normal hearing are documented in the literature (Hussain, Gorga, Neely, Keefe, & Peters, 1998).
- Distortion Product Otoacoustic Emission (DPOAE): One level of L1 and L2 65/55 dB SPL for at least four frequencies. Normal distributions for this condition for normal hearing are documented in the literature (Gorga et al., 1997).
The audiologist is responsible for ensuring regulatory compliance prior to conducting testing. Regulatory requirements identify specifics and required documentation. Familiarization to the test tone before threshold measurement is not recommended.
If unilateral hearing loss is suspected, the audiologist uses appropriate masking, rules out testing errors, and verifies proper function of the audiometer and transducers. In instances of atypical threshold responses, such as identical thresholds in both ears or unusual configurations, the audiologist considers reinstruction and/or retest to verify threshold accuracy and verifies proper function of the audiometer and transducers.
Stimuli: Continuous, warble or pulsed tone signals are used. Pulsed tones have been shown to increase a test participant's awareness of the stimuli (Burk & Wiley, 2004).
Transducer: Earphones (supra-aural, circumaural, and insert) used for pure tone audiometry shall be appropriate to the test technique used. Transducers are matched to the audiometer and should not be interchanged without recalibration. Supra-aural and insert earphones are appropriate for air-conduction threshold measurements from 125 Hz through 8000 Hz, while circumaural earphones are used for extended high-frequency measurements within their respective frequency and intensity response ranges.
- Diagnostic testing: Thresholds are typically assessed at 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz, except when a low-frequency hearing loss exists or is suspected, in which case the hearing threshold at 125 Hz is also measured. Inclusion of 3000 Hz and 6000 Hz frequencies in routine testing of air-conduction thresholds may provide the audiologist with a more complete profile of the patient's hearing status for prevention and diagnostic purposes (Fausti et al., 1999; Holmes, Niskar, Kieszak, Rubin, & Brody, 2004; Humes, Joellenbeck, & Durch, 2005).
When abrupt differences of 20 dB or more occur between adjacent octave frequencies, additional frequencies may be added at the discretion of the tester (ANSI, 2009).
Order: The better ear, when known, is tested first. Initial test frequency is typically 1000 Hz. Following the initial test frequency, the audiologist tests at, in order, 2000, 3000, 4000, 6000, and 8000 Hz, followed by a retest of 1000 Hz before testing at 500, 250, and 125 Hz. A retest at 1000 Hz is not necessary when testing the second ear. Presentation order of frequencies does not significantly influence test results (ANSI, 2009). The above order is an arbitrary choice that will ensure consistency of approach and minimize risk of omissions.
Masking: Air-conduction pure tone audiometry can be confounded by crossover or contralateralization of the signal, which occurs when a signal presented to one ear, if it is of sufficient magnitude, is perceived by the other ear. Interaural attenuation is the reduction in sound energy of a signal as it is transmitted by bone conduction from one side of the head to the opposite ear. Interaural attenuation for air conduction can range between 40 and 80 dB. Masking should be used if the difference in air conduction in the test ear and bone conduction in the non-test ear is 40 dB or greater. The type and level of masking are noted on the form on which the test results are recorded.
Transducers: Bone vibrators are used for bone-conducted threshold measurements for frequencies within their respective frequency response ranges and must meet the specification of Mechanical Coupler for Measurement of Bone Vibrators (ANSI, 2002). Standard bone-conduction vibrator placement should allow mastoid or forehead placement with proper force applied (Dirks, 1964). The test ear should never be covered or occluded for standard bone-conduction measurements. The contralateral ear will be covered or occluded when masking is being used.
Frequency: Thresholds are measured at octave intervals from 250 to 4000 Hz and at 3000 Hz. When testing is performed for bone conduction at 250 Hz and 500 Hz and thresholds are obtained in the 35 and 55 dB HL range, there is a high probability that the responses were a result of tactile rather than auditory stimulation (Roeser, Valente, & Hosford-Dunn, 2007). Suspected vibrotactile responses are noted on the audiogram form. Higher frequencies may be tested if the transducer has sufficient frequency-response characteristics.
Order: The initial frequency used for testing should be 1000 Hz. After the initial test frequency, the audiologist should test at 2000, 3000, and 4000 Hz, followed by a retest at 1000 Hz before testing at 500 and 250 Hz.
Masking: Typically, if the unmasked bone-conduction threshold is 10 dB or greater than the air-conduction threshold at that frequency in either ear, masking is used. Because the threshold values on which the calibration of bone vibrators is based were measured with masking noise in the contralateral ear, the audiologist may prefer to always use masking in the testing procedure. The type and magnitude of the masking sound should be noted on the form on which the test results are recorded.
The chart below offers potential test modifications for issues encountered during pure tone audiometry. The modifications are not intended to be comprehensive in scope or ideal for all situations. Sound clinical judgment is always paramount.
|Developmental age of the patient
||Age-appropriate test modifications, such as visual reinforcement audiometry, conditioned play, conditioned orientation response, or computerized audiometry, may be used.
||Tell the patient how to exit the booth or test with the booth door ajar. If the door is left open, consider use of insert earphones to minimize effects of ambient noise.
|Exaggerated or non-organic hearing loss
||Consider reinstruction, counseling, and reexamination. In compensation cases, ascending threshold technique may be used.
|Collapsed ear canal
||Insert earphones, support the pinna from behind to prevent the collapse, or test with the participant's mouth open ( Reiter & Silman, 1993).
||Use pulsed signal or a warble tone to help distinguish the test signal from the tinnitus.
|Physical limitations for motor response
||Modify motor response task or use verbal response task.
|Severe/profound hearing loss
||Begin testing with low-frequency pure tones.
|Difficult to test
||Reinstruction, counseling, and reexamination are valid strategies. Use alternative objective measures (e.g., ABR). Modify behavioral procedures as appropriate to cognitive abilities. Repeat familiarization task at test frequencies other than 1000 Hz, when responses are inconsistent.
Speech audiometry includes speech awareness/detection thresholds, speech recognition thresholds, word recognition testing, and sensitized speech testing (filtered, compressed, speech in noise, etc.) and is used to evaluate hearing sensitivity and speech perception ability and for site-of-lesion testing.
A speech threshold test quantifies an individual's hearing threshold level for speech. Agreement between the speech threshold and the PTA should be -/+7 dB. The option to substitute a Fletcher average (the two best frequencies) is appropriate when the hearing loss is sloping (>15 dB/octave) in configuration. Clinically, the primary purpose of a speech threshold test is to serve as a validity check for the pure tone audiogram.
Speech Threshold Definitions
Speech Recognition Threshold (SRT). The speech recognition threshold is the minimum hearing level for speech (ANSI, 2010) at which an individual can recognize 50% of the speech material. Speech recognition thresholds are achieved in each ear. The term speech recognition threshold is synonymous with speech reception threshold. Spondaic words are the usual and recommended test material for the speech recognition threshold. Other test materials can be used. If so, then the test material should be noted in recording and reporting the results.
Speech Detection Threshold (SDT)/Speech Awareness Threshold (SAT). The SDT/SAT is the minimum hearing level for speech at which an individual can just detect the presence of speech material 50% of the time. The listener does not have to identify the material as speech, but must indicate awareness of the presence of speech sounds. The material used to obtain a speech detection threshold should be noted in recording and reporting the results.
General Considerations for Clinical Determination of the Speech Threshold
When circumstances or individual capabilities prevent determination of a speech recognition threshold (SRT), the speech detection threshold (SDT), sometimes referred to as speech awareness threshold, may be determined instead. The SDT will occur at a lower level than the SRT, because the SDT depends on audibility alone, whereas the SRT requires that a patient both hear and identify the speech signal. Threshold of detection can be expected to be approximately 5 to 10 dB better than threshold of recognition.
The type of speech material is not as critical for this measure, because it reflects detection and not recognition. Some common materials are speech babble, running speech, or familiar words. Nevertheless, specification of the type of material helps to ensure test-retest reliability and may be useful information for future hearing evaluations.
The usual response mode for obtaining the speech recognition threshold is repetition of the stimulus item. For patients for whom it is not possible to obtain verbal responses, alternative response modes are needed. Many alternatives are acceptable but must convey recognition of test items from a closed set of choices. For example, response modes can take the form of picture pointing, signing, or visual scanning. In addition, if a picture-pointing task is used for obtaining the speech recognition threshold, then the clinician should be cautious in choosing the number of response items. Too few items increase the probability of chance performance, and too many items may be distracting and increase response time (e.g., a number between 8 and 12 words is usually appropriate). The audiologist considers behavioral, cognitive, and language issues that may impact a patient's testing results.
For assessing the speech detection threshold, a number of response modes can be used to convey signal detection. Usually, these response modes are nonverbal. Whenever a response mode other than repetition of a spondaic word is used, it should be specified in recording and reporting the results.
The basic procedure for determining speech recognition thresholds consists of instructions, familiarization, a single series of descending threshold determinations, and calculation of threshold hearing level.
Either a recorded or a monitored live voice technique can be used to obtain the speech threshold. Recorded presentation of the test material is the preferred procedure. When monitored live voice is used, it should be noted with the test results.
Techniques for establishing an SRT include:
Technique A (after Downs & Minard, 1996)
- Familiarize the patient with the spondees.
- Present one spondee at the lowest attenuator setting (or 30 dB below an SRT established during a previous evaluation). Ascend in 10 dB steps, presenting one word at each level, until the patient responds correctly.
- Descend 15 dB.
- Present up to five spondees until (a) the patient misses three spondees, after which you should ascend 5 dB and try again, or (b) the patient first repeats two spondees correctly. This level is the SRT.
Technique B (after Huff & Nerbonne, 1982)
- Familiarize the patient with the spondees.
- Present one spondee at a level approximately 30 dB above estimated threshold. If the patient does not respond correctly, increase the intensity by 20 dB. If the patient responds correctly, decrease the level by 10 dB.
- Continue to present one word until the patient does not respond correctly. At this level, present up to five words. If the patient identifies fewer than three words, increase the level by 5 dB. If the patient identifies three words, decrease the level by 5 dB.
- Threshold is the lowest intensity level at which three out of five words are identified correctly (Stach, 2010).
Masking: When the obtained speech recognition threshold (or speech detection threshold) of one ear exceeds the apparent speech recognition threshold (or speech detection threshold) or a pure tone bone conduction threshold at either 500, 1000, 2000, or 4000 Hz in the contralateral ear by 40 dB or more, masking should be applied to the non-test ear. The appropriate masker for a speech stimulus must have a wideband spectrum (e.g., white noise or speech-spectrum noise). The level of effective masking used should be sufficient to eliminate reception by the non-test ear without causing overmasking and should be recorded on the same form as that used to record audiometric results.
Word recognition scores are obtained for each ear using phonetically balanced (PB) monosyllabic words and are expressed as a percent correct. There are several word lists available.
Testing may be terminated after 10 words, if no errors occur, or after 25 words, if there are no more than four errors. Otherwise, the full 50-item list is administered (Runge & Hosford-Dunn, 1985).
Masking: Masking is used for word recognition testing when the presentation level in the test ear exceeds the best bone conduction threshold in any of the speech frequencies for the non-test ear (500, 1000, and 2000 Hz) by 35 dB or more (Roeser et al., 2007).
Either a recorded or a monitored live voice technique can be used to obtain the word recognition score. Recorded presentation of the test material is the preferred procedure, as it standardizes the composition and presentation of the test list, allows for better control of the intensity of the test items, and ensures that the speech pattern of the recorded talker will be consistent for each client. When monitored live voice is used, it should be noted with the test results.
Specific considerations are given when evaluating the speech recognition skills of non-English and limited English proficient (LEP) speakers. Monolingual audiologists may not be able to appropriately administer and monitor tests developed in other languages, whether presented in live voice or pre-recorded. Reducing the test set size by including only familiar words may result in inaccurate threshold measurements. Alternative measures of speech recognition have been developed, such as using paired digits as stimuli. This measure has been found to accurately evaluate the hearing threshold for speech in non-native English speaking adults and to closely match the pure tone average (PTA) threshold. The services of a trained interpreter/translator may be needed to obtain the most accurate word recognition scores. However, it is not appropriate to simply translate English materials. Test materials must reflect the phonetic balance of the patient's language.
A number of self-assessments are available to measure the level of disability or handicap caused by the hearing loss in a patient's everyday life and provide an individualized assessment of specific situations that cause communication difficulty to the patient. Measuring the extent to which a hearing loss is limiting or restrictive provides the audiologist with additional information about the patient's communication needs and motivation and serves as an outcomes measure or as a baseline assessment against which to compare the eventual benefits gained from hearing aid amplification. See
self-test for hearing loss.
Auditory brainstem response (ABR) testing is used mainly to diagnose hearing loss in difficult-to-test patients and for differential diagnosis of cochlear hearing loss versus retrocochlear hearing loss, specifically tumors of cranial nerve VIII. Auditory evoked potentials, originating from cranial nerve VIII and auditory brainstem structures, consist of five to seven identifiable peaks that represent neural function of the auditory pathways and nuclei. The ABR is a sensitive indicator of functional disorders of the VIIIth nerve and lower auditory brainstem and is often the first test of choice if a disorder is suspected.
The ABR component waves, especially Waves I, III, and V, are easily recordable in many cases and are very reliable in terms of their latency. Although absolute numbers will vary across clinics, the latencies are relatively stable across individuals. The I-V interpeak interval in most adults is approximately 4 msec, and the standard deviation of this interval is about 0.2 msec. Thus, 95% of the adult population have I-V interpeak intervals of 4.4 or less. If the I-V interval exceeds this amount, it can be considered abnormal (Stach, 2010).
Click stimuli at a high level (e.g., 80-90 dB nHL) is adequate in most situations to identify Waves I, III, and V. If no response is obtained at the maximum output level, the audiologist obtains one run of rarefaction clicks and one of condensation clicks to distinguish between cochlear and neural dysfunction. A catch trial (i.e., signal running but not delivered to the ear) can rule out a stimulus artifact that may be misinterpreted as the cochlear microphonic (CM).
Measurements that are used include
- comparison of Wave V latency with distribution of normal values;
- interaural comparison of peak latencies
- If the difference in value of the Wave V peak latency between ears is greater than .2 ms, test is positive for a tumor (Selters & Brackmann, 1977);
- comparison of interpeak latencies (I-V and I-III) with distribution of normal values;
- interaural comparison of interpeak delays.
Note: Cochlear pathologies are typically associated with a delay of Wave I.
Measurements that are used include
- comparison of Wave V amplitude with distribution of normal values,
- interaural Wave V amplitude comparison,
- comparison of Wave V/I amplitude ratio with distribution of normal values,
- interaural Wave V/I amplitude ratio.
When behavioral audiometric tests are judged to be unreliable (i.e., non-organic hearing loss), ear-specific thresholds cannot be obtained, or results are inconclusive regarding type, degree, or configuration of hearing levels, threshold testing-such as ABR, bone conduction, or ASSR-may be used as part of the assessment process to predict hearing thresholds.
Predicting hearing sensitivity using ABR involves determining the lowest intensity level at which an auditory evoked potential can be identified. Click or tone-burst stimuli are presented at an intensity level that evokes a response. The level is then lowered, and the response is tracked until an intensity is reached at which the response is no longer observable. This level corresponds closely to behavioral threshold.
Stimuli: Frequency-specific stimuli are tone bursts of low, mid, and high frequencies.
Transducer: A complete audiologic evaluation includes both an air-conduction and bone-conduction ABR, when indicated. Insert earphones are recommended, unless contraindicated, for air-conduction testing.
Bone-conduction thresholds are established in a manner similar to air-conduction thresholds, but with a different transducer. A bone vibrator is used to generate vibrations of the skull and stimulate the cochlea directly. In theory, thresholds by bone conduction reflect function of the cochlea, regardless of the status of the outer or middle ears.
Note: Responses are typically attempted down to 20 dB nHL in at least 10 dB steps.
The auditory steady-state response (ASSR) is an auditory evoked potential, elicited with modulated tones that can be used to predict hearing sensitivity in patients of all ages (Dimitrijevic et al., 2002; Rance & Rickards, 2002). The response itself is an evoked neurological potential that follows the envelope of a complex stimulus. It is evoked by the periodic modulation of a tone. The neural response is a brain potential that closely follows the time course of the modulation. The response can be detected objectively at intensity levels close to behavioral thresholds. The ASSR can yield a clinically acceptable, frequency-specific prediction of behavioral thresholds.
Stimuli: Frequency-specific stimuli are amplitude- and frequency-modulated pure tones with typical carrier frequencies of 500, 1000, 2000, and 4000 Hz.
Transducer: Insert earphones are recommended, unless contraindicated, for air-conduction testing. A bone-conduction transducer will be needed if air conduction is elevated (i.e., if air-conduction thresholds are greater than 20 dB nHL, bone-conduction testing is completed to assess the type of hearing loss).
Note: ASSR analysis is mathematically based. The specific method of analysis to define threshold is dependent on the manufacturer's statistical detection algorithm.
It is essential that all audiometric equipment be calibrated, be functioning properly, and be used in an acceptable test environment to ensure accurate test results as specified in American National Standards Institute/Acoustical Society of American (ANSI/ASA) Standard s3.6-2010.
Equipment And Calibration
Equipment and transducers are to meet applicable specifications of ANSI/ASA S3.6-2010 (ANSI, 2010), ANSI S3.39-1987 (ANSI, 1987), and manufacturer specifications and be appropriate to the test technique being used. In addition, exhaustive electroacoustic calibrations are to be performed annually using instrumentation traceable to the National Institute of Standards and Technology; functional inspection, performance checks, and bioacoustic checks are conducted daily to verify equipment performance prior to use (ANSI, 2010).
- Use of specific transducers may be dictated by a particular regulatory standard, such as the use of insert earphones for audiometric monitoring under the Occupational Safety and Health Administration (OSHA) hearing conservation amendment (1983). The applicable regulation should be consulted before testing to ensure compliance.
- The audiologist controls placement of the transducers on the listener.
Test environments should meet the specifications detailed in Maximum Permissible Ambient Noise Levels for Audiometric Test Rooms (ANSI, 2003). In addition,
- audiometric test rooms typically include visual and/or auditory warning systems connected to the building warning system (fire, civil defense) and are equipped with an emergency telephone or a panic button to signal for emergency assistance;
- mobile phones, pagers, radios, and other communication devices are silenced or turned off during the audiometric evaluation;
- the test room and audiologist's work area provide for proper control of temperature, air exchange, and humidity.
Confirmation of an acceptable test environment should be documented at least annually.
Adherence to universal precautions and appropriate infection control procedures should be in place. Instrumentation coming into physical contact with the patient must be cleaned and disinfected after each use. Disposable acoustically transparent earphone covers or disposable insert earphone tips are recommended, and clinician hand washing between patients should be routine (Siegel, Rhinehard, Jackson, Chiarello, & the Healthcare Infection Control Practices Advisory Committee, 2007). See OSHA standards relating to
occupational exposure to bloodborne pathogens and the Centers for Disease Control and Prevention's
universal precautions for preventing transmission of bloodborne infections.