**3. Clinical applications**

#### **3.1. Otosclerosis**

Otosclerosis is a disease that affects the ME and causes progressive hearing loss, occurring predominantly in women (predominant age range 20–30 years). In most cases, the disease manifests bilaterally through calcification and an abnormal growth of the Stapes. In patients with otosclerosis, the absorbance measures can identify an eardrum-ossicular system rigidity with more details. During the progression of the disease, the fixation of the stapes in the oval window worsens, making the ME transmission of energy very difficult [17, 27].

WBT provides more detailed and specific information on the eardrum‐ossicular system and allows a differential diagnosis of otosclerosis. According to the data from Shahnaz et al. [18], the most prominent change in the absorbance pattern following an otosclerosis surgery is a sharp and deep drop in absorbance values in the range between 700 and 1000 Hz. There is also a secondary wider and smaller increase in absorbance, following the surgery, between 2000 and 4000 Hz. **Figure 4** shows a typical absorbance profile of an otosclerosis patient. The peak absorbance value has been shifted to higher frequencies, approximately at 2.8 kHz.

**Figure 4.** The characteristics of the absorbance graph (which is obtained by collapsing the pressure axis in the 3D-WBT graph) of the case of a patient presenting otosclerosis.

#### **3.2. Immittance in neonates**

frequency of the middle ear tends to be reduced. In the case of otosclerosis, the resonance frequency shifts to higher frequencies [17, 18]. Monitoring the resonant frequency seems to be promising as a method to follow the clinical progression of otosclerosis. It is also possible to obtain the "resonance frequency tympanogram," which is useful in the differentiation

From the 3D-WBT graph, it is possible to obtain information about the absorbance at a particular frequency measured in ambient pressure or at the pressure of the middle ear (see Appendix section for a video showing how this is accomplished). The acoustic absorbance (A) is defined as the ratio of (absorbed sound power)/to (incident sound power). Pathologies that can be further monitored or identified with this data modality are: otosclerosis, flaccid eardrums, ossicular chain discontinuity, and semicircular canal dehiscence and babies with negative middle ear pressure and middle ear effusion [20, 21]. The WBT devices from Mimosa Acoustics utilize the concept of acoustic reflectance. Reflectance is the amount of energy reflected by the system in relation to total energy propagating through the system, and it is measured in percentage. The reader might find useful terminology reviews by Hall and

Several publications indicate that the graph of absorbance allows a better differentiation between middle ear diseases than the traditional tympanometry. There are groups of patients where the pressurization of the ear can be difficult or unwise. Thus, an absorbance test held in nonpressurized conditions will be useful for monitoring middle ear state immediately after surgery, with perforated eardrum during neonatal hearing screening. In several studies performed in ambient pressure proved to be able to detect changes in middle ear function significantly for infants and neonatal measurements [23, 24]. In the case of patients with ventilation tubes in the eardrum, data from Groon et al. [25], suggest that: (i) for any leak larger than 0.25 mm there are absorbance alteration effects up to 10 kHz; (ii) above 1 kHz these effects are unpredictable; and (iii) absorbance values were mostly increased in the lower frequency

Data from Keefe and Simmons [26] suggested that the absorbance measurements, if they are conducted at peak pressure level, are more sensitive to ME pathologies and complications. Analytically they have reported "comparing tests at a fixed specificity of 0.90, the sensitivities were 0.28 for peak‐compensated static acoustic admittance at 226 Hz, 0.72 for ambient‐pressure WBT, and 0.94 for the pressurized WBT. Pressurized WBT was accurate at predicting conductive hearing loss with an area under the receiver operating characteristic curve of 0.95."

Otosclerosis is a disease that affects the ME and causes progressive hearing loss, occurring predominantly in women (predominant age range 20–30 years). In most cases, the disease manifests bilaterally through calcification and an abnormal growth of the Stapes. In patients

between cases of ossicular disruption and a flaccid eardrum [17–19].

Chandler [5] and by Stinson [22].

34 Advances in Clinical Audiology

bands (0.1–0.2 and 0.2–0.5 kHz).

**3. Clinical applications**

**3.1. Otosclerosis**

Growth and thus changes in auditory canal occur rapidly in the first 6 months of life when they reach adult size. Among the possible outcomes in neonatal hearing screening program, there are false positives that may result from differences in the development of ear structures that harm the impedance mechanism [23, 28]. Due to the presence of amniotic fluid, meconium mesenchyme or the external auditory canal may cause temporary changes in hearing. These alterations increase the mass, stiffness, and resistance of the eardrum‐ossicular system and consequently alter the middle ear of impedance and efficient sound of conduction [29, 30].

At birth, the neonatal external and middle ear are not fully developed. The external auditory canal is surrounded by a thin layer of elastic cartilage [31]. When performing the pressurization, as occurs in typical tympanometry, the diameter of the external auditory canal can increase or decrease depending on the applied pressure. As the infant grows, the ossification of the external canal increases its rigidity. It also increases the length of the canal, which decreases the canal's resonance frequency [23]. The eardrum will eventually decrease in thickness, will increase in size, and will modify its inclination. Changes occur in the ME as well. Data from Proctor [32] and Holborow [33] show that the neonatal Eustachian tube is shorter [30 mm], and almost horizontal [32]. The Eustachian tube opens effectively but closes more slowly, resulting in tubal inefficiency. The Eustachian tube develops slowly reaching full maturity at the age of 7 years with increased length and steepening. This may explain higher prevalence of otitis media associated with upper respiratory tract infections in early childhood [33, 34].

A number of studies have shown [23, 28, 35] that the majority of the significant modification to the values of wideband absorbance occurs is the first 6 months of life, due to the development of the external and middle ear. During this period, there is an "absorbance immaturity" at low frequencies and an absorbance significant increase in the high frequencies. After this period, the absorbance measurements start to approach the absorbance values reported from adult subjects. **Figure 5** shows a typical neonatal average absorbance (0.8–2.0 kHz) curve, from an infant who has passed the neonatal screening TEOAE test.

**Figure 5.** Example of wideband averaged tympanogram in a neonate with a normal function ME and a PASS from the TEOAE assessment.

Because of the difference in the size of the ear canal, between an adult and a neonate, the absorbance measurements between these populations differ considerably. In the neonates, absorbance shows low values at the low frequencies and then a decrease approximately at the frequency of 6.0 kHz [36–38]. The latter also depends on the stimulus bandwidth. Some commercial systems like the Titan from Interacoustics use a stimulus bandwidth of 8 kHz.

as occurs in typical tympanometry, the diameter of the external auditory canal can increase or decrease depending on the applied pressure. As the infant grows, the ossification of the external canal increases its rigidity. It also increases the length of the canal, which decreases the canal's resonance frequency [23]. The eardrum will eventually decrease in thickness, will increase in size, and will modify its inclination. Changes occur in the ME as well. Data from Proctor [32] and Holborow [33] show that the neonatal Eustachian tube is shorter [30 mm], and almost horizontal [32]. The Eustachian tube opens effectively but closes more slowly, resulting in tubal inefficiency. The Eustachian tube develops slowly reaching full maturity at the age of 7 years with increased length and steepening. This may explain higher prevalence of otitis media asso-

A number of studies have shown [23, 28, 35] that the majority of the significant modification to the values of wideband absorbance occurs is the first 6 months of life, due to the development of the external and middle ear. During this period, there is an "absorbance immaturity" at low frequencies and an absorbance significant increase in the high frequencies. After this period, the absorbance measurements start to approach the absorbance values reported from adult subjects. **Figure 5** shows a typical neonatal average absorbance (0.8–2.0 kHz) curve,

**Figure 5.** Example of wideband averaged tympanogram in a neonate with a normal function ME and a PASS from the

TEOAE assessment.

36 Advances in Clinical Audiology

ciated with upper respiratory tract infections in early childhood [33, 34].

from an infant who has passed the neonatal screening TEOAE test.

Many references in the literature, i.e., [36–38], use and report reflectance values in their WBI assessment. **Figure 6(A)** and **(B)** shows normative neonatal data from reflectance and absorbance curves (10–95 percentiles). The reader can see that the reflectance curve can be deduced from the inverse of the absorbance curve.

**Figure 6.** (A) This graph shows the normal Reflectance zone (25–75 percentiles) for neonatal WBT responses, as reported by Silva et al. [37]. The reflectance curve shows low averaged values (<25%) at the mid frequencies 1.0–2.0 kHz. Two peaks are shown, one at approximately 0.5 kHz (65%) and the other at 5.0 kHz (55%). Due to the fact that different systems were used for the generation of (A) and (B), the data in (A) are not perfectly inverse of the data of (B). (B) This graph shows the normal absorbance zone (10–90 percentiles) for neonatal WBT responses, in the Titan device. The absorbance curve shows low values (<50%) at frequencies <1.0 kHz and above 6.0 kHz. Two absorbance peaks are shown one at approximately 2.8 kHz (85%) and 5.0 kHz (82%).

### **4. Consensus on the terminology and research objectives**

During the 2012, Eriksholm Workshop [39] sponsored by the Oticon Foundation (November 5–7, 2012), an array of consensus statements was developed, regarding the emerging field of wideband immittance measurements. These are summarized below:

