How Do You Hear Without ‘Ears’?

How Do You Hear Without ‘Ears’?

History’s littered with lost ears: Van Gogh’s, Evander Holyfield’s, that ear Kyle MacLachlan finds in a field in Blue Velvet, and so on. Or maybe ears is the wrong word. The weird little flesh-whorls that jut out from the sides of most of our heads are just small components of a much larger, delicately interconnected system. Remove part of that system with a razor-blade upon learning that your brother is getting married, and you risk seriously compromising it.

Illustration: Sam Woolley (Gizmodo)

The question is: To what extent? Is the external ear – known, in professional circles, as the pinna or auricle – something nice to have but ultimately cosmetic, like a pinky toe? Or would losing one fundamentally impair your ability to hear? For this week’s Giz Asks, we reached out to audiologists and otolaryngologists (that is, ear, nose and throat doctors) to discuss the auricle’s function, and what life might be like without one (or both). The good news is, you can definitely hear without them – but, for a number of reasons, you might want to think twice before pulling a Van Gogh.

Christopher Fundakowski

Assistant Professor, Otolaryngology – Head & Neck Surgery, Lewis Katz School of Medicine at Temple University

The auricle, or external ear, actually does have an important role in hearing – both in terms of sound amplification and localisation. It essentially serves to collect sound and funnel it from the external environment into the ear canal. The conchae (inner portion of the auricle) and the external ear canal have unique resonant frequencies of approximately 5300Hz and the 3000Hz, respectively, which result in an amplification of these incoming sounds (by up to 10 -15 dB) which are of particular importance in conversational speech. With regards to localisation, the auricle is angled to preferentially collect sound from in front of an individual, and this is particularly helpful in the higher frequency ranges.

The auricle also has protective role, helping to prevent foreign bodies from entering the ear and damaging the tympanic membrane (ear drum). So if someone loses one or both external ears, they’re going to have a mild hearing loss and a harder time localising high frequency sounds.

Aniruddha Deshpande

Assistant Professor, Department of Speech-Language-Hearing Sciences, Hofstra University

The auricle/external ear – which we call the pinna – has different landmarks on it. If you touch your pinna, you’ll notice there are indentations, ridges, elevations – it’s not a flat structure. Those are there for a reason. The main one is to collect sound and transmit it to the external auditory canal, or the ear canal as we call it, so that you can pick up as many sounds as you can, and then direct them to the tympanic membrane via the ear canal.

I teach Introduction to Audiology here at Hofstra. One activity that I do in my class is, I’ll play a single frequency sound, a pure tone, and then have my students cup and uncup their ears with their hands. If you do this yourself, you’ll notice that the tone sounds louder when you’re cupping your ears – and that’s exactly what the function of the pinna is. It collects all those sounds and delivers them to the ear canal. When you cup your pinna, you’re extending its length.

There are a couple of things that would happen [if one or both of your pinnae were lost or damaged]. The ability to collect sounds would be minimised – though you wouldn’t completely lose that ability – and amplification would be reduced. Typically the pinna and the ear canal together amplify sounds by anywhere between 5 to 10 dB; if your ear canal and pinna were damaged, you’d lose that.

Typically we talk about [the pinna and the ear canal] together – they make up the outer ear. The ear canal is a cylindrical structure, so it has a resonant frequency, and that resonant frequency happens to be between the speech frequencies that are important for us to communicate with each other. If it were destroyed, then that ability would be minimised.

Olivia Galioto

Clinical Audiologist at Precision Hearing

Your auricle (pinna) is part of the outer ear system. It is the piece of cartilage and skin surrounding the ear canal. The pinna acts as a funnel to direct sound waves into your external auditory canal and is particularly useful for high frequency sounds. If you were to lose your pinna, you would still be able to detect and hear sounds; however, your ability to localise high frequency sounds would be decreased. To compare, dogs are better able to localise and detect a wider frequency range compared to humans partly due to the size and shape of their ears. They also have the ability to swivel their ears towards the sound they are trying to focus on, which enables maximum hearing proficiency.

The pinna only acts as a small part of your overall hearing system. Once sound is collected from the pinna, is it funnelled into your external auditory canal which then sends the sounds waves to your eardrum (tympanic membrane), causing your middle ear bones (ossicles) to vibrate. These vibrations cause the fluid inside your cochlea (inner ear) to move and this in turn activates your hair cells, which then sends the signal to your auditory nerve. Your auditory nerve then delivers the message to your brain which we interpret as sounds. Damage to any of these systems will cause an attenuation in your hearing ability, but there is a wide range of severity based on the degree of injury.

Keith R. Kluender

Professor and Department Head, Speech, Language & Hearing Sciences, Hofstra University

Sounds arriving at the eardrum (at the end of the ear canal) will be somewhat fainter because the pinna (auricle) works like an acoustic funnel for sound waves.

The person would have greater difficulty detecting the elevation (how high or low relative to person) of sounds in the environment. This is because the shape of the pinna increases/decreases relative energy at some frequencies versus others depending on elevation of the sound source. The brain uses these changes in frequency composition to figure out how to look up or down to see what is heard.

Shruti Deshpande

Assistant Professor, Communications Sciences and Disorders, St John’s University and the Long Island Audiology Consortium (Adelphi, Hofstra and St John’s Universities)

Our auricles play a crucial role in processing sounds. Our ability to localise sounds (or understand the direction of the sound source) depends, to a great extent, on our auricles. I teach ‘Hearing Science’ and I often set up a fun experiment. A volunteer with no hearing-related complaints sits on a chair, blindfolded. I snap my fingers around one meter from the volunteer’s body (for example, at different angles above, below, in front of and behind the volunteer’s head), and he/she is requested to point as accurately as possible, to the sound source. Often times the volunteer performs with 90 to 100 per cent accuracy. Next I perform the same task, but this time around by asking the volunteer to place their palms around their auricles, thereby minimising the auricles’ participation during this part of the experiment. When the auricles’ can’t participate, the response accuracy on this localisation task drops to approximately 50 per cent. My students are often amazed by the localisation ability of the auricles after this experiment. You could easily try this experiment for yourself.

In addition to localising sounds, the auricle and the ear canal have evolved to boost sound energy in the 2000-4000 Hertz frequency range in humans. Human beings predominantly communicate via speech and this frequency range is crucial for listening to various speech sounds, especially the consonants which carry the bulk of the speech information. No wonder if you plug your ear canals with your fingers, you may not be able to understand speech clearly.

Since the auricle develops in the first trimester of pregnancy, aberrations during embryological development can lead to absent auricles (anotia) or deformed auricles/ear canals (microtia, atresia). Fortunately, advances in medical science and audiology can significantly help individuals with such disorders.

Charles J. Limb

Francis A. Sooy Professor, Chief of Division of Otology, Neurotology and Skull Base Surgery, Director of Douglas Grant Cochlear Implant Center, Departments of Otolaryngology-Head & Neck Surgery and Neurosurgery, University of California San Francisco School of Medicine

In humans, the auricle (or pinna) is involved in hearing but not required for hearing. In the event of losing your auricle, there are a few immediate effects. One is a small drop in volume, as the auricle helps to collect sound and direct it towards the ear canal. The auricle also helps the brain concentrate on a source of interest (generally in front of the listener) by reducing the impact of background noise. One of the most important functions is related to sound localisation in the vertical plain. In other words, the presence of the auricle improves your ability to identify where a sound is coming from in the up/down axis. In normal hearing, both ears work in concert together to provide binaural effects of amplification, summation, noise reduction, and localisation of sounds. Injury to the structures of the ear (auricle, ear canal, eardrum, hearing bones, inner ear) or central auditory system (auditory nerve, brainstem, cortex) will all affect hearing to various degrees depending on the nature and extent of the damage.