- Posts
During a DOGRADIO STUDIO 2 FM transmitter check,
I decided to try something I had never done before.I was trying to calibrate the VU meter on my Gates
During a DOGRADIO STUDIO 2 FM transmitter check,
I decided to try something I had never done before.I was trying to calibrate the VU meter on my Gates
board to the FM deviation meter on my Kenwood
KT-8300 FM tuner. This would make it easier for
me to know that the audio chain was working
correctly, and that the station wasn’t over deviating.The Gates board VU meter is being driven by a
radio, so I can see the compression and limiting
of the air signal audio that is taking place. So, I
did all I could to make the readings from the 2
meters agree with each other.After fooling around with it for a while, I realized
YouTube has videos with calibration tones. So I
started with 440 Hz, and then went to other audio
frequencies from there. Then I did an EQ of the
various components.I got things pretty much where I wanted them to be
but imagine my shock – I put a 10,000 Hz tone through
the system. The meters were pinning, but I heard:NOTHING.
It turns out that I can hear up to about 8,000 HZ. But
only in my right ear.It must be from years and years of AM broadcast band
DXing, where I would crank up the headphone volume
to hear some far away station. Then I would play back the recording
of it over and over and over until I figured out what the
callsign was. A lot of times I NEVER figured out what I was
hearing.And then there was the DXing on the graveyard channels – you
know – the locals on 1230, 1240, 1340, 1400, 1450, and 1490.I love those channels. But apparently my ears didn’t.
I have been doing a little bit of listening on my AM crystal set
lately. I’m glad I can still hear that. During the big storm,
the crystal set was great because it needed no power source,
so it saved batteries.Still, I’m bummed a little bit about my ear’s frequency response.
But at least I can still hear the tiny bit of audio from a crystal
receiver’s headphones.What can you hear?
If nobody wants to try it, I don’t blame you!
Best Wishes,
Bruce, DOGRADIO STUDIO 2
Total posts : 45366To sum up my situation, the wife says GET HEARING AIDS OR ELSE…
Total posts : 45366Hi Bruce. Interesting subject you bring to the forum.
The very highest note on the piano is about 4.1kHz, and I think the piccolo maybe goes a little higher, but everything way above that is mostly upper-harmonics, which add to the richness and realism of the sound.
Your doctor might be able to restore your ear by simply removing debris that could be blocking the upper range. This is a common situation.
Here is a chart of piano key frequencies.
Total posts : 45366MRAM – Oh yeah, I think I need a hearing aid.
And to Carl – I’ll have to show that chart
of piano frequencies to my son.He is a very good musician, but he doesn’t
seem to have any understanding of the
audio spectrum. He just knows that “A”
is 440 HZ.Best Wishes,
Bruce, DOGRADIO STUDIO 2
Total posts : 45366Keep in mind also that unless you were monitoring the line level audio directly through the studio monitors, you probably wont hear much of a 10khz audio tone from the radio unless that radio was in wide band mode.
Remember most AM radios brick wall the audio at about 6khz. This is not saying that you may not have a hearing issue, but should not be ruled out that there is something blocking the “upper” end already and it has nothing to do with your ears.
Adding: In fact if I was you, I would wire up those meters via one of the on-board AUX switches and flip those meters between “AIR” meter and “LINE” meter.
RFB
Total posts : 45366I was listening to (or trying anyway) the audio
tones through the studio monitors, which are
in stereo, and in the beginning of the program
line. The AM and FM transmitters are mono.
AM is not on now, although I am starting to wire
it back up.As the Gates board evolves, I do plan to have the
VU meter be switchable between “air” and “line”
and that sort of thing.Next time you get over to Carl Blare’s website – you
might want to take a look at the pictures that are
associated with the Low Power Hour programs. Not
too far under the pictures from you – the great CC
installation – you will see my Gates board. I added
a cuing speaker on the front of the board since I always
wanted one. It is blue in color. The actual speaker in
it is very small, but it works OK. It just can’t be overdriven.
I’ll have to make a provision so that can never happen.That picture of the board was taken with the unit sitting on
a couch. Since then, the board has been placed in the
station operating position. Unfortunately, the Gates VU meter
was destroyed (by me) when I was trying to adjust the lights
in it. I have another, slightly smaller VU meter in there now,
which looks OK the way I have it set up. That VU meter is
from another board, from another station. (By the way, I
appreciate all the comments about replacing VU meters,
that I received on that other thread.)Best Wishes,
Bruce, DOGRADIO STUDIO 2
Total posts : 45366I would have left the board on the couch. Call it Cozy Radio.
Total posts : 45366I remember in biology, I was taught that human beings could hear from 20Hz to 20Khz.
BUT, that’s only when we’re very young (3-4 years old) and it’s downhill from there.By the time we reach teenage years, it tops out around 15Khz, then down to 10Khz to 12Khz by the time we’re in out late 30’s.
Bottom line is if you’re looking for speakers and insist on a 20Hz to 20Khz range, you’re wasting your time.
Andre
Total posts : 45366I just checked the hearing of my
19 year old son. His upper range
is about 15,000 HZ.So that goes along with the info you
just sent.Cool.
Bruce, DOGRADIO STUDIO 2
Total posts : 45366Several weeks ago on another thread, maybe on another forum, (it was called “Stereo and Mono”) I pleaded with a Pt. 15 FM operator who was thinking of disabling his stereo generator and 15khz audio filter, so he could broadcast those “audio frequencies between 16khz and 20khz for higher fidelity sound”. I begged him and everybody else NOT to do it. Now you know why! At least now you know ONE of the reasons why. There are TWO! Anybody know what else happens when you pull that stunt?
Total posts : 45366by eliminating the 15 khz filter he would cause a lot of splatter on the fm band. That filter would allow upper frequencies that would eat a lot of bandwidth and cause adjacent channel interference??
Again i am guessing here.
Total posts : 45366Pulling the 38khz crystal to kill the 19khz pilot and 38khz L-R sub carrier won’t kill the 15khz roll off filter in the audio chain. That is way before the MPX circuitry.
And yes if that audio front end did not have a roll off filter at 15khz, the audio would beat frequency the 19khz detector in the receiver and flash in and out along with the stereo indicator. The result would be a splatter or highly distorted upper frequency response in the audio.
Hopefully no one will bypass that roll off in their TX. No reason to. It has nothing to do with killing the stereo or recovering bandwidth and range.
RFB
Total posts : 45366“I remember in biology, I was taught that human beings could hear from 20Hz to 20Khz. BUT, that’s only when we’re very young (3-4 years old) and it’s downhill from there.”
Speak for yourselves!!
In most yes. But not in everyone. Are you or anyone else aware that part of our ability to hear the frequency range is the shape of our outer ear.
It is like a megaphone. The shape focuses certain frequencies, particularly the higher frequencies, into the ear canal like how a parabolic snooper dish works. These are used quite a lot on the football field on each side to listen in on what the other team is planning. It is also how the field sounds during play are picked up.
Anyway back to hearing 101.
Now….do you live in a congested city? If so..when was the last time the local environment police did a sound measurement of ambient noise?
Does your 19 year old drive around with the thumper bumper rattling the trunk lid woofer blasting 170dB of 40Hz and below, literally over-working the delicate inner ear components..stressing them out to the point of degradation…meaning reduction in hearing sensitivity.
As the Op said at the beginning..all those years with the headphones on and volume cranked up listening to distant AM stations along with the static, pops, crackles and whistles, its no wonder your hearing went south.
Does anyone remember back in the real days of education they taught us all how the ear has the ability to attenuate certain loud sounds in order to protect it, but that natural hearing protection is limited and can degrade rapidly if the ear is exposed to too much loud noises. Wonder why after hearing loud sounds or noises your ears ring? Duh! Each day of exposure to loud noises, some of which have peaks in amplitude that would literally blow your ear drum out if you watched it on a scope. In other circumstances, the peaks would over load or exceed the highest setting of the scope.
Now amazingly the opposite is true as well. Living in quiet environments helps preserve the hearing. Wearing hearing protection if you know you will be around loud noises helps too.
Those who take care and try to prevent long exposure to excess noise tend to have far better hearing than those who do nothing to protect their hearing.
Last REAL hearing check I got from my doctor showed I still have the hearing range I had when I was a kid. I can hear from 15hz out to 22khz, and I am MUCH older than 30.
I do not blast my ears with static noises from listening to distant stations every night. I do not expose myself or my toddlers (if I had a toddler), to 170+db of dirty mouth street rap rattling every vehicle and building in a half block radius, when advised or noted on a sign near a construction site or area where loud noises are common, such as an airport or train station or subway station, I wear ear plugs to protect my hearing.
Now here is something that none of you probably even considered, but has been investigated by independent researchers.
Go look at the statistics for hearing losses in people overseas, particularly those living in villages and small communities. Their hearing is superb, far exceeding our rankings in retaining hearing ability.
Isn’t it curious that the data reported about hearing leveling off at 15khz? Stop and think about WHY…WHY 15khz.
What were all of us exposed to for decades until the recent change over to digital?
And what frequency did the old devices used for decades operate the HV at???
OOOHHHH lemme guess……the TV?
YES!!!
I remember when working at a Sony service center years ago, senior citizens calling me up asking me why do they hear this strange noise coming from their television set. Low and behold it would be the set’s 15khz horizontal circuitry causing the flybacks to oscillate and mechanically vibrate which would generate a 15khz audible noise.
Now how the heck could 70+ year old folk be hearing that without hearing aids if their hearing went to poof at 13??
Amazingly though, the opposite is true as well. I would do service calls to senior citizens homes to to follow up checks on their televisions, and there were quite a few who could not hear their television screeching at them, but I certainly could, as did some of their younger family members.
The whole point here is that you can throw out graphs and charts all day long and they do not mean a damn thing when it comes to each persons unique abilities, including hearing range and sensitivity. It is no different from two individuals of the same stature, but one can run a bit faster than the other, or carry a tune better than the other, or hold their breath longer under water than the other.
Not everything is so straight and narrow just because its on some chart.
I suggest if you want to really know what your hearing range is currently at, go to a real hearing doctor and get a REAL hearing test done, using the proper hearing test equipment and in the proper testing environment before declaring everyone is deaf.
Or if you want to be adventurous, build yourself an ultrasonic emitter gun operating 30Khz @ 90db and after you get up off the floor come back and tell me your hearing stops at 15Khz!
RFB
Total posts : 45366In a recent thread we discussed the Aphex Aural Exciter, an interesting device which “restores” upper harmonics to faded recordings, especially in the analog reel-to-reel or audio cassette realm, where multiple generations of tape copying caused the high end to roll-away. The Aural Exciter is especially useful for restoring old-time radio recordings which have been passed through generations of dubbing and re-dubbing.
Another audio claim I have heard, although I can’t remember who said it or wrote bout it, is the claim that well-produced CD record quality is better than FM radio quality. If that is true, which I’m not sure about, it might have to do more with the signal-to-noise ratio (range from loudest to softest) rather than the frequency response, but maybe someone knows more about that.
Total posts : 45366Trust me Carl, your gonna find that the CD’s frequency response curve is FAR greater than that of FM.
Now go find an older CD..say one that was put on the market back in the late 80’s, when 99 percent of the master recordings were analog tape and transferred over to digital for the CD’s. On EVERY CD jewel case on the back it would have the following note:
“The music on this Compact Disc was originally recorded on analog equipment. Due to the high resolution of the Compact Disc, it can reveal limitations of the source tape.”
I don’t suppose anyone really remembers reading that? Well that right there tells you that the CD’s resolution is FAR greater than the master analog tapes as well as it being superior to FM’s frequency response.
This is why back in the day of early CD’s, many FM operators found it quite annoying to see and hear the stereo going in and out in sync with the high frequencies from the CD, until they realized that they needed a much harder brick wall filter to keep that high resolution audio from beating against the 19khz pilot.
Now throw in the even HIGHER resolution of the HD CD or DVD-A.
Why would the recording industry produce such high resolution media, 6 channels of it in some cases, if our hearing range stopped at 8khz???
I have an idea! Remove all of the tweeters elements from your speakers and leave only the woofer and mid-range and tell me if you noticed a difference if your hearing only goes out to 8 or 10 khz!!!
RFB
- You must be logged in to reply to this topic.
