Hear Birds Again

by Lang Elliott (1670 words)

Hello everyone! My name is Lang Elliott and I am a professional nature recordist and bird enthusiast who suffers from severe high frequency hearing loss that prevents me from hearing the songs and calls of a great many birds. For over thirty years, I have worked hard to find an optimal solution, both for myself and others who suffer from the same affliction. Mine has been a long and drawn-out effort that has culminated with the recent publication of Hear Birds Again, a free, open source application for Apple mobile devices, described in full on our website, hearbirdsagain.org.

Lang Elliott listening for birds at the edge a meadow in early autumn. Photo © Melissa Groo

The purpose of this essay is to elucidate the problem, share the rationale behind possible solutions, and celebrate the completion of our new app. Please read on to learn what the fuss is all about, but also be sure to check out “My Story” in the colored insets, which describes my personal journey to find the best solution, an adventure spanning a period of 45 years

The Problem – High Frequency Hearing Loss

As we humans grow older, we experience diminished sensitivity to high frequency sounds. Youthful hearing extends as high as 20,000 Hz (Hz = cycles/second and kHz = 1000 Hz). However, the average person over fifty or sixty years of age (especially among men) has completely lost the very highest frequencies and suffers significant loss in the range from 4-10 kHz (4,000 to 10,000 Hz). Sadly, moderate to severe hearing loss above 4-5 kHz is the norm for most individuals living to sixty and beyond.

Loss of hearing with age, a condition technically referred to as “presbycusis,” is a widespread phenomenon that seemingly cannot be avoided. To make matters worse, prolonged exposure to loud music and other loud background sounds also results in reduced sensitivity in the high range (even among younger people). This is NOT good news for aging birdwatchers for the simple reason that most birds (especially songbirds) are difficult to spot and are generally discovered and identified by hearing their songs, the majority of which are in the high range.

Diagram showing presbycusis, hearing loss due to aging.

The average frequency of the songs of songbirds is around 3.5-4 kHz, approximately the same pitch as the highest note of a piano. Many warblers, sparrows, waxwings, kinglets, and a number of other birds produce songs that reach 8 kHz and above. It follows that significant hearing loss in the 3-10 kHz range will make it difficult if not impossible to hear the songs and calls of a great number of species in typical outdoor situations … a painful outcome for those attempting to bird by ear!

Cape May Warbler 7-8 kHz

Given the growing popularity of birding and all the amazing technological advances in this modern world, one would think there are a number of elegant solutions to high frequency hearing loss, but it turns out there are none that specifically address the needs of birders, with the notable exception of our Hear Birds Again app. But before delving into the workings of our app, let’s take a brief look at other approaches to the problem.

Blackburnian Warbler 5-11 kHz

The Amplification Solution

The traditional approach to counteracting hearing loss has been to utilize amplifying hearing aids that raise the amplitude of incoming signals to levels where they can be heard. In modern times, this is accomplished by super high-tech electronic hearing aids that work well in the realm of speech perception (mostly below 3 kHz) but usually have limited application for birders who suffer from high frequency hearing loss.

Small and inconspicuous, modern hearing aids are truly a technological marvel, but will they bring back the high-singing birds?

For aging birders, conventional amplifying-type hearing aids are often a major disappointment. Some of the problems encountered are summarized as follows:

1) There is a limit to how much a hearing aid can amplify before feedback squeal occurs. If hearing loss is severe, maximum amplification will not be adequate to allow high bird songs to be heard at reasonable distances in typical outdoor situations.

2) Extraneous sounds such as wind noise or the sounds that accompany walking through leaves or stepping on twigs are also amplified and can be extremely annoying. Users often complain of “sensory overload” due to the continuous high-level amplification of environmental sounds.

3) Even when users wear amplifying aids in both ears, the ability to determine distances and directions of incoming sounds is normally much reduced. The three dimensional or “binaural” aspect of hearing is greatly compromised and it becomes difficult, if not impossible, to find birds, even when they are heard.

4) The ability to enjoy the “softness” of distant bird songs is entirely lost. When extreme amplification is applied, softer sounds are boosted to high levels in order to be detected. And when they are detected, they are perceived as being “very loud,” even though they’re not. This can easily overwhelm and disorient the senses.

5) Amplifying-type aids generally “plug the ears” in order to create a tight seal to reduce the possibility of feedback squeal. This not only feels uncomfortable but also prevents users with intact hearing in the lower ranges from enjoying the wide and spacious immersion of their extant natural hearing.

Prairie Warbler 4-7 kHz

In spite of the problems described above, amplification-type aids can certainly be helpful to those with moderate hearing loss, especially when models are used that specifically advertise exceptional high frequency response.

Until very recently, such “prescription” hearing aids were quite expensive, costing several thousand dollars each and involving numerous visits to an audiologist. But now, with FDA approval of OTC (over the counter) hearing aids suitable for mild to moderate hearing loss, one may purchase a high-quality entry-level aid for as little as $500 (and possibly less).

So, if your hearing loss in the range from 3-8 kHz is “mild to moderate” (around 30-40 decibels of suppression on an audiogram), the amplification approach might be worth trying. But remember there is no guarantee that amplification aids will be truly useful in actual outdoor situations, where the ability to hear and locate faint and distant bird sounds is all-important for a satisfying and pleasurable birding experience.

Winter Wren 3.5-8 kHz

Our Pitch-Lowering Solution

Given that potential users have moderate to severe hearing loss above around 3 kHz yet still have fairly good hearing in the lower range up to around 2-2.5 kHz, a totally different approach to bringing back the high singers can be employed … and that is to pitch-shift high bird songs into the lower range where they can heard without the need for amplification. As you might guess, this is exactly what our Hear Birds Again app does, giving the user control over what frequencies are shifted and the degree of pitch-lowering that is applied.

Hear Birds Again – Primary App Controls

Furthermore, by using our app in conjunction with a loose-fitting, open-air “binaural” headset, the lowered bird songs can be seamlessly added to the soundscape the user is already hearing, without impairing the user’s still-useful hearing range. There will be no plugging of the ears (as occurs with amplification aids) and the resulting mix will sound so real that the user will have difficulty distinguishing a pitch-shifted bird song from one that is being heard naturally.

Our open-air binaural headset is equipped with low noise mics mounted on earphones that rest lightly on the ears and do not obstruct one’s normal hearing.

You may wonder how Hear Birds Again accomplishes the frequency shifting. Briefly, incoming bird sounds are received by tiny mics positioned on the headset at each ear, and then routed into the mobile device, where they are converted into digital signals. Our app then selectively pitch-lowers the high-range songs using advanced algorithms tailored specifically for this purpose. Finally, the pitch-lowered songs are fed back to each ear via the headset, where they are then “mixed” with the natural soundscape one is already hearing.

There are a number of approaches to frequency division and several well-known algorithms are currently available for our use. While we have already developed and implemented our own algorithm that allows for several pitch-shift settings (one-half, one-third and one-quarter), we also intend to add more advanced solutions that will provide considerably more control over the amount and quality of shifting.

Field Sparrow 2.5-5 kHz

In conclusion, our Hear Birds Again mobile application, when used in conjunction with our recommended binaural headset, will allow for the preservation of a natural, three-dimensional listening experience where the pitch-lowered songs will be transparently mixed with sounds one is already hearing. The lowered bird songs will be heard at normal or near-normal levels and users will be able to determine their directions and distances, making it possible to actually find and observe the singers.

Because pitch-lowering does not involve extreme amplification, extraneous sounds like the rustle of leaves or the snapping of twigs will not be annoying. There will be no uncomfortable plugging of the ears. Furthermore, sensory overload will be completely avoided, feedback squeal will not occur, and the overall effect will be gentle, natural, and spacious.

Although our currently recommended headset is admittedly bulky in comparison to modern amplification aids and also requires a wired connection to your iPhone, we believe the potentially excellent results will far outweigh the downsides. Hopefully, in the near future, more compact wireless options will become available.

You may wonder if you’ll be able to recognize the pitch-lowered songs. While it is true that the frequencies have been lowered, pitch-relationships within songs, overall character of sound (timbre), and timing of delivery remain intact. A Black-throated Green Warbler will still say see-see-see-soo-zee and a Black-and-White Warbler will still go wee-see-wee-see-wee-see. Although some pitch-lowered songs will indeed be difficult to identify, at least at first, many others will be instantly recognizable. In the end, however, dealing with potential problems related to pitch lowering is a small price to pay when one considers the alternative, which is not hearing the high-pitched singers at all.

For detailed information about our app and the headset, plus numerous audio examples of pitch-lowered songs, please visit our website, hearbirdsagain.org.

Photo © Melissa Groo