On several occasions I have been asked to give some advice or suggestions to radio amateurs who have impaired hearing. The last occasion was a young man who is almost deaf, but he does still have some weak hearing sense remaining. Running solely digi-modes is not always so rewarding: after while you can get bored with relying on the computer as the sole means of communicating. There are, however, other methods that can be used to assist your hearing and regain some of the functionality of analogue radio. A lot depends on your degree of deafness and your engagement to overcome the impediment.
It is quite normal for people to become to some degree deaf with age, and my first experience in this matter was in the late 1960s when my uncle Arthur could no-longer hear the television. In order to hear the TV he had to screw the volume up REALLY LOUD, but he never heard the neighbours banging on the walls. My auntie was also plagued with excessive volume. My uncle resigned himself to a life without TV sound. This was ok to watch the "Tiller Girls" on "Sunday Night at the London Paladium", but not much good when trying to follow "The Sweeney" (a UK detective series).
So I fitted a pair of HiFi headphones to the TV and used a resistive splitter to feed the TVs internal loudspeaker and the new headphones. I also fitted a 3-pole power socket and an isolation transformer so that the headphone outlet was earthed. Just a simple safety precaution.
When Arthur next wound up the volume to the normal cacophony it hurt. It was too loud for him. He had to reduce the volume a lot and was able to hear the TV without disturbing the neighbours, or his wife.
As a radio amateur the problems can be similarly easily fixed, or perhaps treated in a slightly different manner.
With age, the ear sensitivity falls, typically by about 10db to 20dB at 1kHz. According to the governments, frequencies above 8kHz do not matter and if you have only 10dB loss at 1kHz then you are considered to be fit. My own hearing is good to about 15kHz, but it is not flat. I have about 8dB loss at 1kHz, which I believe is quite good. At 10kHz I have about 20dB loss, but this is also quite reasonable and useable.
"Communications quality headphones" have a limited frequency response as they only need to reproduce 300Hz to 3.5kHz. So instead of using your ICOM or YAESU communications headphones, couple the output of your radio to the HiFi stereo amplifier and plug in a pair of HiFi headphones. HiFi headphones have several qualities that can be of use: They can block out your surrounding background noise from the TV and family, so that you can concentrate more on the sounds from the HF radio.
These HiFi headphones usually have a much greater signal handling property in order to give a good dynamic range (good for listening to Beethoven?). This aspect you can use to turn the volume up a lot and get a sound that is easier to listen to. They often have a small loudspeaker inside the headphone capsules, so they can take a watt or so of audio.
I recently found a pair of "Bose" noise-cancelling headphones in the electronic rubbish skip. Someone had spilled coffee on them and it had begun to ferment. I put the ear-pads and protective cloth in the washing machine and they now look like new. The actual headphone chassis was washed in fresh water, as was the speaker elements, which have a plastic cone. They work perfectly. When I switch ON the phones it is like I go totally deaf. All background noises dissapear. At first it was a bit un-nerving as my own voice was also attenuated, but you soon get used to it.
It is normal to use communication quality headphones with HF radio. These often operate up to about 4kHz. Even for a normal person there is a noticeable roll-off with frequency. If you have an impaired high frequency response then these will only make matters worse. In the days of SW and MW radio the upper frequency limit was only 4.5kHz, but by emphasising the treble frequencies you can get an effect of a wider frequency response.
So once again, instead of using your ICOM or YAESU communications headphones, couple the output of your radio to your stereo amplifier and plug in a pair of HiFi headphones. If you have a graphic equaliser then you can push up the HF response by typically 20dB, and even reduce the bass by 20dB. In effect you can get a percieved 30dB to 40dB improvement in your hearing frequency response. This should be more than enough for most people.
To detect CW more easily there are a few other tricks you can we, especially if you have independant Left and Right volume and tone controls on your HiFi stereo amplifier. You can feed both channels with the same (monaural) signal but adjust the left-hand channel for high bass response, and adjust the right-hand channel for high treble response. The crossover should be about 750 Hz. This will spread the audio spectrum (0-4kHz) out in front of you and give you a spacial sound display. Different audio frequencies will appear to come from different directions. As you tune through a CW signal you will hear the tone move from left to right, or the other way, depending on which way you tune the radio. Several different simultaneous CW signals will each have their unique position in the stereo image.
You can also use a simple 1:1+1 audio transformer and drive both channels in opposite phase, which will cause a cancellation in the middle and make sound appear to come from the sides. This trick can also be used to help you pick out audio CW tones.
If your ears are not the same then the balance control can be used to balance your hearing so that you can get some resemblance of normal symetry.
With all of these suggestions you may find it of benefit to use CW filters, but with a decent graphic equaliser you may find the CW filter of little or no help whatsoever.
You can feed the headphone signal, via a 0.1uF capacitor, to the base of BC547 or 2N2222. An LED with 220 Ohm resistor in the collector will then flash in sympathy to the incoming audio. In this event the LED will flash quite nicely when you receive CW signals, especially if you have the CW filter switched ON. You can decode CW without hearing anything at all, or simply use the LED as an aid in the corner of your eye whilst listening. Vision can supplement your hearing in this way.
Another trick is to use your sense of touch. The old speaker from a defunct AM/FM radio can be connected in parallel with your radio speaker and placed in your shirt pocket. Have the diafragm placed against your chest. In this way you will still have your hands free for operating and writing, but you can also feel the sound on your chest. You will not normaly damage the diafragm (unless of course you are YL ;-).
From Windows VISTA onwards, MS operating systems also have an in-built speech recognition program. I have begun using this with hamradio, not because of a hearing defect, but because I can turn down the volume at night and let the computer display speech to text. The quality is not very good, but since the vocabulary is so small the program has little difficulty in displaying speech. You tend to see the same "garbage" text time and time again, but when I read "see queue doggies ray" it takes little imagination to realise that the spoken words were "CQ Dog X-ray".
When someone has difficulty hearing oneself speak through bone conduction, pronunciation can become a little different making it harder for the other person to understand your speech. It can be even more difficult for other hamradio operators to understand the spoken word over 10,000 km, with QRM, and through a little 2" speaker. In this event it can be an idea to use the HiFi once more and put on those headphones. Turn up the treble and use a microphone to listen to your own voice while you speak.
Pronunciation can be improved with a little practice, even if you do not have any hearing difficulties. English spoken by a non native English speaker can often sound somewhat strange as I found out when I started learning Swedish. To be perfectly honest I think that some New Zealanders could use the training.
But joking asside, it is often difficult to hear your own speech when speaking a diffferent language. I have used this technique as a training aid when speaking Swedish. Just try listening to a native English speaker trying to say "Sju sjuka sjukskorteskor".
Now you may think that this is a bit tasteless, but you can have a bit of fun with loss of hearing. I found this out by accident when I wanted to deter cats from comming into a particular area of the house. So I bought a nice little 10-Watt tweeter (discant) loudspeaker and connected this to a crude multivibrator and audio amplifier. I adjusted the frequency so that I could not hear anything because the frequency was too high, then I screwed the volume up to maximum - 10 Watts.
It worked a treat! It was too uncomfortable for the cats acute hearing and such high frequencies are particularly uncomfortable for them. But what I did not appreciate was that my own hearing response hadfallen and that tone I could not hear was only about 16kHz. Unfortunately most of the guests to our house COULD hear it excruciatingly plainly. Maj-Lis and I wondered why people often wanted to leave our house quickly.
One more point of interest is that people who can hear the tone have trouble identifying the source. So if you download a Signal Generator APP for your iPhone then you can have a lot of fun on the commuter train or the underground railway. You can even add a little something extra to your door-bell with a tweeter outside the front door.
Just imagine the burglar alarm you could make? A little 150-Watt AF amplifier could scare the shit out of unwanted guests, and even phantom doorbell ringers (the local kids).
If you can think of any good uses or more ways to have fun with this then please let me know. I can post it here.
Did you know that spiders have ears in their legs?
Yes, it's true, and you can prove it:
Put a spider on the desk in front of you, then when he has settled down you make a sharp loud noise (like klacking together two pieces of wood). Little "Spidey" get frightened when he hears the noise and he gets up and run away.
Now pull off all the spiders legs and repeat the experiment. Spidey does not move at all, thus proving that if you pull all a spiders legs off it becomes deaf.
Best regards from Harry - SM0VPO
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