A busy flock of Golden-crowned Kinglets the other day first got me thinking about birdsong and the physical ability to hear it. The kinglet calls were just barely audible to me, but it’s because I heard them my attention was drawn to where they were hopping around in a patch of spent thistles by the roadside. Without hearing their faint high psees I’d have walked right on by, as my husband would surely have. He has presbycusis, otherwise known as high-frequency hearing loss, partly due to his age (70s), partly exposure to loud noise when younger (he’s a USMC vet and a car guy). Sadly, he can’t hear many of the sounds of nature, which means missing out on much of what’s going on. He compensates partly by visual acuteness and awareness. But he’s just one of many folks whose hearing limits his birding, and in fact we will all eventually be faced with the loss of birdsong. What causes HF hearing loss, how does it affect what we hear, and is there anything that can be done about it?
First, let’s brush up a bit about sound. Sound travels in waves, which are variously big or small (=loud or soft, amplitude) and high or low pitched (=how fast air particles vibrate, measured by the frequency of waves passing a fixed point, in Hertz) (if you’re interested in learning more about sound, or anything sciency, I recommend watching the really wonderful Khan Academy YouTubes; here’s his intro on sound: www.khanacademy.org/...).
Loudness is usually measured in decibels, a logarithmic scale, meaning sound intensity goes up much faster than the numbers. 30dB is a whisper, 50dB a normal conversation, 80dB is yelling and over 100dB unpleasant/painful unless you’re into such things as jet engines, sirens, gunshots or heavy metal concerts. Loudness is a factor of how close you are to the source and for most of us the loudness of wild birds is comparable to that of human voices (link.springer.com/...). Some birds are extremely loud, like roosters, peacocks and parrots, all of whom show up in studies at over 100dB, but they are exceptions. In noisy environments like cities birds sing louder out of necessity to be heard by others of their kind, much as we humans do at a party, but in nature we hear birds comfortably.
The pitch range of birdsong is mostly between 1000-8000 Hertz (= 1-8 kHz) which is exactly what we humans hear best (www.allaboutbirds.org/...). Human hearing range is usually defined as 20Hz — 20,000Hz (or 20kHz) but that upper limit is largely academic since it is quickly lost after our early 20s. Functionally, we can only hear those higher frequencies if the volume is turned way up, if at all. The diagram on the left shows the putative 20kHz range that requires even young ears to have a screaming volume to hear that higher end. A normal conversational loudness — for both people and birds — limits our range to 15kHz for young ears and 10kHz for typical middle-aged ears. For the audibly acute elderly, 8kHz is the limit at best. Fortunately, most birdsong is within our range even so.
However more often than not presbycusis affects our hearing as we age to some degree, and even 8kHz is inaudible to many. That means we don’t hear the upper range of birdsong, if we hear it at all. The loss of higher pitch changes how birdsong sounds. The following diagram shows typical audiogram results for a person with presbycusis after being tested by an ear/nose/throat doctor. The steeply dropping lines (left and right ears) indicate the volume that would be required to hear the pitch. A normal-hearing person’s lines would go straight across at 20dB. This person doesn’t even hear the lowest frequencies as well and the higher frequencies would require volumes far louder than either people or birds talk. That portion of their words is inaudible.
In addition, everything sounds fainter in general, meaning a sound would have to be 10-20dB louder just to hear it as well as a person with normal hearing. My husband can’t hear low-pitched owls at a distance because the sound is too faint for him. Closer — ie louder — he’d hear it.
What’s it like to listen to birdsong when you are partially deaf like this? Tim Traver at his blog Northern Woodlands described it this way:
For example, I no longer hear Louisiana waterthrush, a harbinger of spring on our brook. At first, I thought they weren’t nesting.
northernwoodlands.org/...
I try to imagine what it would feel like one spring not to hear a Robin or Red-winged blackbird, wondering if they had disappeared for good, and how could it really be spring.
A sonogram (also called a spectrogram) shows how Golden-crowned Kinglets are inaudible to someone with presbycusis like my husband, who can’t hear above 2kHz. The vertical scale is calibrated 0 — 5kHz — 10kHz like all the sonograms I’m posting here from xeno-canto (www.xeno-canto.org/...). The comma shaped smudges between 8-10kHz are the kinglet’s song (the general darkness at the bottom is background noise). The kinglet is just barely audible to me; my high-frequency loss isn’t nearly so bad.
And for a Wilson’s Warbler and a Violet-green Swallow:
Some songs don’t become completely inaudible, but that isn’t much comfort. According to Chelle, young woman who developed presbycusis in her 20s, it’s like trying to converse with people: “I can hear you talking...but I can’t understand what you’re saying.” (www.saywhatclub.org/...). A birder may hear a bird singing but can’t understand the song’s melody or pacing or timbre, ie what makes the song distinctive, because they’re only hearing fragments. A couple of examples you can listen to for comparison are found in this column at Earbirding: earbirding.com/…. Audio clips there demonstrate how a Carolina chickadee will be mistaken for a Black-capped chickadee, and the tone of a Carolina gnatcatcher is muted and dull.
We can sort of “hear” what would be missing in the songs of the following birds (like the ones above, locals in my neighborhood). See how much of the song is above 2 kHz:
The music and vibrancy would be gone in their songs and calls, even if an occasional thump came through. It’s like listening to a symphony orchestra when all you can hear is the percussion and lowest notes.
What can a hearing-impaired birder do, not to lose the world of bird songs and calls? In the arena of technology, Tim Traver suggests:
1. Conventional hearing aids can be modified to amplify sound at only the higher frequencies, thus avoiding the problem of sensory overload.
2. SongFinder by Nature Sound Electronics converts high frequencies to digital signals, then divides and lowers them. You hear the lost songs only when they sound lower – like a record playing at a slower speed.
3. Another product is a mobile app that picks up songs via the mic on your smartphone and converts them to graphic sonograms – the sheet music of birdsong.
northernwoodlands.org/...
An example of the latter is Spectrogram, for IOS devices. The visual images are in color. This is an example captured by Alma Schrage, a deaf ornithologist who tells her story at this blog page: toughlittlebirds.com/…
There are low tech ways partially deaf folks can continue birding and not miss out because they can’t hear well. You can birdwatch with someone who hears better, who will cue your attention to where a visually elusive bird may be. “Over there in the snowberry bush! There’s a warbler.” You can become more visually acute and aware in general, as my husband is. He notices anomalies quite a bit better than I do, and drawn my attention to a new bird at the feeder more than once.
If you’re not profoundly deaf you probably can still hear in the lower frequency range. Some birds naturally have low voices, and you can focus on their songs and calls. In general larger birds have lower frequency calls. Jays, ravens, owls, woodpeckers, doves, pigeons and wild turkeys may be partly or fully audible.
You can probably already predict what a big owl’s call would look like on a sonogram, but even a Pileated woodpecker has a surprisingly low voice.
A good birding destination for birders who want to hear them as well as see them is aquatic habitats. Ducks, geese, swans and loons all have deep voices. Even a duck that sounds squeaky, like a wigeon or bufflehead, calls mainly below 2kHz. You may miss out on the rich harmonics of a Trumpeter swan, but you’ll know it’s there at least.
If you are hearing-impaired, you already know what you are missing out on, and experience the frustrations of telephones, conversations, doorbells, alarm clocks and such. If you are young and unimpaired, and want to be able to hear for many years to come, here’s a tip: REDUCE the loud sounds you are exposed to, like music, movie theaters, traffic, sirens, aircraft, lawn mowers, leaf blowers, crowds. Physically, we hear things when the vibrations of sound waves trigger the tiny sensory hairs of our inner ears via the eardrum, ear bones and cochlear fluid (www.nidcd.nih.gov/...). Loud sound damages those hairs, not just sudden extreme noises like gun shots or sirens, but also the cumulative effect of long-term exposure to moderately loud sound. Once the sensory hairs in your inner ear die, they’re gone for good. You lose your hearing permanently.
We’ll all gradually lose our hearing as we age but noise will accelerate that irrevocable process, and a young person today will be as deaf as their grandpa at a much younger age. The corollary of that is they will be hearing-impaired for a much larger part of their life.
There’s a double insult to birders with presbycusis who live in urban settings. Not only are they exposed to more noise, which further destroys hearing, but the background noise of traffic etc drowns out the relatively fainter sounds of birds. And on top of that, there is plenty of research showing that birds in noisy environments actually change the pitch of their calls upward to be heard over the ambient racket. Blackbirds, Robins, Song Sparrows and Great Tits are a few examples. In the diagram below, the sonograms are of (a) rural tits, (b) urban background noise, (c ) urban tits. Note how the city birds' call is shifted higher. For a high-frequency hearing-impaired birder these birds will be even harder to hear.
Some birds are unable to shift their song higher, and depart a site altogether, like the Black-headed Grosbeaks, Mourning Doves, Western Tanagers and Scrub Jays at BLM property in New Mexico where compressors run constantly in a natural gas extraction area (phys.org/...). If birds can’t establish territories and attract mates they won’t nest. They go elsewhere if they can.
So, my fellow birders, as we close down another calendar year, each of us another year older and a little less able to hear, let’s give thanks for the senses we still have. I am personally thankful I can see pretty well and can hear not too badly and am able to get outside most days for a while to where birds live in natural quiet habitats. I live in a semi-rural area, even if I’m buzzed by Navy jets now and then, and mostly what I hear is nature, including birdies. Especially in winter after the tourist season has closed down. But I can empathize with folks who are less able, or who have farther to go to spend some time with birds. If you know folks who’d love to do more birding but feel limited by their hearing, or otherwise, share some time or ideas that might make birding more accessible. If you know young people who have the birding bug, or show an interest in nature, see if you can find a way to communicate how lucky they are to be able to hear the song of a Golden-crowned Kinglet, and how they might hang onto that gift.
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P.S. Here’s an amazing fact about hearing:
Did you know birds don’t go deaf? If they damage their cochlear sensory hairs, new ones grow back. This is true for amphibians and reptiles also. Only mammals go permanently deaf (stanmed.stanford.edu/…).
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Any insights or suggestions to share with the group about birding while hearing-impaired?
What birds have you seen this past week in your neighborhood or travels?