TINY IN SIZE BUT BIG IN SOUND

When it comes to virtually invisible hearing aids, size matters! We pack a lot into a tiny hearing aid because tiny is what our customers want. Here’s how we’re able to deliver big sound quality in a small package.

Choosing the right hearing aids can be overwhelming. Sound quality, comfort, style, price, service – all are important factors to consider. However, when it comes to the physical attributes of a hearing aid, most consumers know what they want. When surveyed, most of those who were already wearing Eargo, or were considering Eargo, ranked invisibility and rechargeability as their most important factors for selecting a hearing aid – which is likely what drove them to Eargo in the first place. No matter what hearing aid product a consumer chooses, good sound quality should be a requirement – not a factor to be ‘considered’. That’s why at Eargo our mission is to deliver great sound quality in an extremely small, rechargeable device. Here’s how we do it.

We start with small parts

Invisible-in-the-ear and rechargeable! That’s a lot to ask of a device as complex as a hearing aid, but Eargo made it happen by partnering with some of the best technology companies in the world. We partnered with Knowles, a market leader and global provider of advanced micro-acoustic microphones and speakers. They already manufacture some of the smallest speakers in the industry, but they made one even smaller for Eargo 5. (figure 1) With a length of only 3 mm, the Knowles’ proprietary speaker fits perfectly in the Eargo 5 case. This tiny receiver was built to cancel vibration patterns, minimize audio feedback, and increase output for clear sound. We also partnered with Varta, a world-leading manufacturer of batteries. Varta custom-designed a rechargeable, lithium-ion cell to fit inside Eargo 5. The cell was actually shaped to fit the contours of the Eargo 5 case. This type of battery provides the highest energy density in the smallest space and is fully charged within four hours.

The miniaturization and customization of the speaker and the battery in Eargo 5 allowed room for other required components such as the microphone and digital signal processor (DSP). They all fit together beautifully and compactly in the final Eargo 5 product 

Next, we take advantage of your ears

The physical shape and geometry of the ear does a lot to help us hear when it doesn’t have a hearing aid in it. The outer ear (pinna + ear canal) (Figure 3) actually amplifies sound before it reaches the eardrum. Most of this natural amplification comes from the ear canal resonance, with a lesser amount coming from the pinna. The pinna has another important function. It has unique sound reflection properties that help us figure out where sound is coming from

So what happens when a hearing aid is placed in the ear? Anything placed in the ear, a finger, an earplug, or hearing aid (when it’s turned off) will physically block some sound from entering the ear canal. If the hearing aid is small and inserted deeply, the ear canal will be effectively shortened but it can still provide some resonance or boost. (middle panel). Eargo 5 leverages that natural boost by leaving a longer portion of the ear canal open. A larger hearing aid with shallow insertion (right panel) will eliminate more of the ear canal’s natural resonance. Note also that when the speaker is deep in the ear, it doesn’t have to work as hard to push the sound out. That’s because the volume of air-filled space between the speaker and the eardrum, called the residual volume, gets smaller as the device gets deeper. This, too, is leveraged by Eargo 5’s deep fit. Finally, the pinna cues that help us localize sound are fully leveraged with Eargo 5 because the microphone sits inside the ear canal. Behind-the-ear styles with microphones that sit behind the pinna, bypass these natural effects. 

In one way or another, the ear’s natural acoustics are compromised by the physical presence of a hearing aid. Any natural ability taken away by the hearing aid must also be restored by the hearing aid. Eargo 5s physical footprint is small, allowing the ear to do more of what it does naturally.

Then we add in the signal processing

Digital signal processing (DSP) is what the hearing aid does to sound after it enters the microphone. The DSPs most challenging function in Eargo 5 is feedback cancellation – the algorithm designed to keep the hearing aid from squealing. Feedback cancellation can be detrimental to the naturalness of sounds, but its function is necessary in order for the hearing aid to remain stable, and therefore wearable. The closer the hearing aid microphone is to the speaker, and the higher the amplification, the easier it is for sound to ‘feed back’ into the microphone. Even with the Eargo 5 microphone and speaker so incredibly close to one another, feedback cancellation is robust enough to allow adequate amplification for mild-to-moderate hearing loss. 

Once feedback is taken care of, the most important function of the DSP is to compensate for hearing loss by using compression and frequency shaping of the input signal. Whether the wearer chooses a factory preset, or completes mobile-phone based hearing assessment and customized fitting (Sound Match™), Eargo 5 can boost hard-to-hear soft sounds without making loud sounds too loud.

Our best sound quality yet

Eargo 5 was released in July, and customers are already telling us it’s our best-sounding hearing aid yet. 87% of Eargo 5 customers who have worn earlier generation Eargos say the sound quality has gotten either much better (66%) or slightly better (21%). With 68% of customers overall reporting extreme satisfaction with sound quality, that says a lot for Eargo 5. Customers can expect Eargo 5 to continue to get even better over time, as both the hearing aid and charger are in-field upgradeable. ChEARS!