WIDEBAND TYMPANOMETRY WITH JACKIE DAVIE, PHD
An excerpt from a discussion with Jackie Davie, PhD on WideBand Tympanometry.
GSI: Let’s start with the basics. What is tympanometry?
Jackie Davie, PhD: Tympanometry is an objective test used to evaluate the middle ear system. It’s been around since the late 1960s and helps us understand how the eardrum and middle ear system respond to changes in air pressure. When the air pressure in the ear canal is at ambient levels, the tympanometer sets this as zero decapascals (0 daPa). The machine then records a graph showing how the eardrum’s compliance changes as the pressure varies from positive to negative.
GSI: How does WideBand tympanometry differ from traditional tympanometry?
Jackie Davie, PhD: The biggest difference is that WideBand tympanometry uses a click stimulus instead of a single frequency pure tone. This click contains a broad spectrum of frequencies, typically from 250 Hz to 8000 Hz, though the system can analyze even beyond that. The key idea is to evaluate how much of that sound energy is reflected back to the probe microphone versus how much is absorbed by the middle ear system.
GSI: What are the advantages of using a click stimulus?
Jackie Davie, PhD: A click stimulus gives us more information that can be used in a comprehensive evaluation of the mechanical properties of the middle ear, especially in the speech frequency range, which traditional tympanometry often misses. It also allows us to measure absorbance across a wide frequency range.
GSI: Has WideBand tympanometry been known by other names?
Jackie Davie, PhD: Yes, over the years it’s been called reflectance, absorbance, and power analysis. But today, we generally refer to it as WideBand tympanometry.
GSI: What exactly is absorbance?
Jackie Davie, PhD: When sounds are introduced into a system, like a room, some of the sound will bounce off the walls, ceiling, and floor while other sounds will get trapped. Absorbance has been traditionally used to measure how much energy is getting trapped in the room. But we can apply the same principle to the ear. If a sound is introduced into an ear canal, some of that energy is absorbed into the middle ear and ear canal while some energy is reflected back. What energy that is not reflected is absorbed meaning that if we think the total amount of energy as being 100%, then the percentage of energy reflected is subtracted from 100%, giving us the percentage of energy absorbed by the middle ear. This percentage is measured at each frequency. So, if 70% of the energy is absorbed at 1000 Hz, that means only 30% was reflected back.
GSI: Can absorbance be measured under different pressure conditions?
Jackie Davie, PhD: Yes! Just like traditional tympanometry, WideBand tympanometry can measure absorbance at ambient pressure, peak pressure, or any other pressure of interest. This flexibility helps us evaluate how the ear performs under various conditions, which can be crucial for identifying specific pathologies.
GSI: What does a typical WideBand result look like?
Jackie Davie, PhD: It’s a graph with absorbance on the Y-axis (0% to 100%) and frequency on the X-axis (250 Hz to 8000 Hz). You will expect to see the first major peak occurring somewhere around 1000 and 2000 Hz. And then you should have a secondary peak associated with it as well. You would expect that the second peak is going to be between 2000 Hz and 4000 Hz. The machine also calculates values like peak pressure and average absorbance, often focusing on the 375 Hz to 2000 Hz range, where most middle ear pathologies tend to have an effect. WideBand also offers better insight into conditions like:
- Changes in stiffness, like otosclerosis
- Changes in mass, like from a cholesteatoma
- Changes in friction, like viscous middle ear fluid or effusion
- Overall sound transmission efficiency
Right now, WideBand tympanometry is also being studied for its ability to predict conductive hearing loss and even estimate its degree, which is incredibly useful in pediatric audiology where bone conduction testing can be difficult.
GSI: What clinical insights can we gain from this?
Jackie Davie, PhD: A lot! It helps bring us back to the basics and focus on mass or stiffness dominated pathologies. Otitis media, otosclerosis, and eustachian tube dysfunction all increase stiffness and friction, reducing absorbance. And on the flip side, conditions like superior canal dehiscence or third window pathologies can increase mass, leading to increased absorbance in certain frequency ranges.
GSI: Are there specific clinical applications where WideBand tympanometry really shines?
Jackie Davie, PhD: Definitely. Four key areas include:
- General detection of middle ear disease
- Verification of pressure equalization (PE) tube function
- Prediction of conductive hearing loss
- Assessment of special populations, especially where traditional testing is difficult
GSI: What kind of practices do you think would benefit from implementing WideBand tympanometry?
Jackie Davie, PhD: WideBand tympanometry offers significant advantages for all types of clinical practices. Its sensitivity to a broad range of middle ear disorders makes it effective across all age groups. Unlike traditional single-frequency tympanometry, WideBand can detect subtle abnormalities that might otherwise go unnoticed.
GSI: Why is this especially useful in pediatric audiology?
Jackie Davie, PhD: In children, it’s often hard to get reliable bone conduction thresholds. WideBand tympanometry helps fill that gap by giving us clues about whether a hearing loss is conductive or sensorineural, based on how the middle ear is functioning across frequencies.
Want to learn more about WideBand Tympanometry? Register for Dr. Davie's webinar series on AudiologyOnline. Visit the courses page to see a full list of available webinars.