Is it my hearing or is it my stereo?

[Jerboy]

I got my hands on a test audio track that sweeps sinusoidal wave from 20Hz to 18,888Hz over a 50 second period and I can only hear from 30-13,800Hz on my Philips stereo(just a mini system, nothing super nice). I stop hearing at 47second. The left speaker connection was hooked up to O'scope. The moment I started and stopped hearing, I hit the "trigger once" button on my scope and stored it on the storage. After spending like 30seconds counting the period on storage view twice, the cycle period of my lowest possible hearing was 3.4 x 10^-02 seconds/29.4Hz and highest was 7.2 x 10^-05/13.9KHz(2µS/div setting).

I'm rather disappoited, because I thought most people can hear 20-20,000Hz, but I can only hear up to 13.9KHz.

There also is a track that is 22,500Hz , the theoretical frequency limit of current 16bit 44,100Hz sampling Compact Disc technology. I can not hear this AT ALL even with volume cranked up all the way, yet registers clearly on O'scope as a sinusoidal wave with cyclic period of 4.44 x 10^-04seconds.



Which is most likely the cause?

A: My hearing is degrading even though I'm only 17.

B: Speakers on $300 system simply can't produce 19,000Hz sound.

C: The scope is lying. Blame Tektronix, their oscilloscope sucks.


Edit: numbers changed a bit. I had the wrong values at first, becuase I mis-read the scope screen. This scope doesn't have read outs other than mV/div and S/div so everything else I have to calculate manually.

 

[Evadman]

Probably your hearing. Highest most can hear is the 15k range. I can not hear anything over about 18k or so. 20k is damn high.

 

[bizmark]

For the upper limit, your hearing. Wish I had an oscilloscope....

The lower limit (30Hz) is more likely to have something to do with the stereo. Could you hear the tones less than 30Hz if you turned the volume all the way up?

Do you have a SPL meter? Then you could tell if your speakers were actually outputting the sound, and gauge the rolloff at the ends.

 

[Evadman]

At 30hz you would more likely be feeling it, not hearing it. everyone is built differently. Humans are machines, ut we are built using cheap labor, as we are not all the same. ( and better because of it )

I don't see how your ossiliscope could be broken belove/below a certan range. If they go, they go all at once.

 

[Stealth1024]

your speakers probably start losing volume past 16KHz

 

[Jerboy]

<< Probably your hearing. Highest most can hear is the 15k range. >>



Really? I always read ranges of hearing for human is 20-20,000Hz so I figured that was the average, many do however mention that upper range fades with aging.

 

[Peter]

A recent study with an African jungle people (who were picked because they don't have loud noise at all) showed
that hearing does not degrade with age - it's all damage from loud noise that accumulates over time in our
industrial world inhabitants' ears.

So Jerboy, you wouldn't be the first 17 year old with symptoms of hearing loss ... so ask yourself a few questions:
How loud do you listen to music? Do you use a portable player often? How much overkill is your car stereo? Do you
use earplugs when attending a pop/rap/rock/whatever concert?
Do you use loud power tools without ear protection? How's your workplace?

regards, Peter

 

[BooneRebel]

Did you buy your stereo with pennies?

 

[bizmark]

It's worth remembering that musical tones and kHz don't line up linearly.

We can hear a whole octave between 20Hz and 40Hz.

The band from 10kHz to 20kHz also encompasses only one octave, even though the absolute range is 10000/20=500 times as large. If you can't hear above 15kHz, you're only losing what, like 3 notes?

Also IIRC the 20-20k figure was set as a rough estimate of the limit of human hearing, not the average.

 

[Elledan]

A somewhat related story:

Some weeks ago during a physics lesson, the teacher set up a tv in front of the class to show a videotape. The moment the tv was switched on, I heard it make a very high-pitched sound (screech). No one else in the classroom seemed to notice anything, even though the sound was very painful. For a few moments I felt the urge to run out of the classroom while covering my ears with my hands, but after realizing how silly it must have looked, I decided against it =)

I've noticed quite often that I'm capable of hearing sounds (high-frequency) other people can not hear. This regardless of the fact that I listen to Metal.

Yes, I know I'm special

 

[Jerboy]

<<
How loud do you listen to music? >>



Usually not that loud. Very rarely I crank it up to floor pouding party level volume.



<< Do you use a portable player often? >>



During a boring lecture I listen to it at low volume. That'll be a few hours a week.



<< How much overkill is your car stereo? >>



Stock and I don't crank it up much



<< Do you
use earplugs when attending a pop/rap/rock/whatever concert? >>



Only when it gets unbearable. I used to go to raves all the time for a year or so on regular basis though.




<< Do you use loud power tools without ear protection? How's your workplace? >>



No I don't. I don't work..

 

[kazeakuma]

Possibly your hearing, if you're worried about it you can get tested. Of course I wouldn't know where you could get it tested, I had mine done at a physical exam for the navy.

Elledan - You too? Damn tvs and crappy monitors piss me off. It annoys and even hurts, depending on how pitched it is. And I listen to Metal too. Must be some link there.....

 

[Stealth1024]

I can hear the high pitched wine of computer monitors running at lower refresh rates and most all TV's

 

[Evadman]

<< I can hear the high pitched wine of computer monitors running at lower refresh rates and most all TV's >>



I can as well. Sometimes, depending on how / where I am facing I can gear a high pitched whine from my power supply as well.

Believe it or not, the "clck" of my stereo wakes me up in the morning, instead of the music when it goes off in alarm mode

 

[Elledan]

<< Elledan - You too? Damn tvs and crappy monitors piss me off. It annoys and even hurts, depending on how pitched it is. And I listen to Metal too. Must be some link there..... >>

Perhaps =)

Whenever I'm inside or near a the entrance to a room in which a PC, TV or similar device is activated, I can hear a very high-pitched tone. With some monitors (keyword being 'cheap' here) I almost go insane from the sound they create. Stupid circuits

 

[CTho9305]

<< A somewhat related story:

Some weeks ago during a physics lesson, the teacher set up a tv in front of the class to show a videotape. The moment the tv was switched on, I heard it make a very high-pitched sound (screech). No one else in the classroom seemed to notice anything, even though the sound was very painful. For a few moments I felt the urge to run out of the classroom while covering my ears with my hands, but after realizing how silly it must have looked, I decided against it =)

I've noticed quite often that I'm capable of hearing sounds (high-frequency) other people can not hear. This regardless of the fact that I listen to Metal.

Yes, I know I'm special >>



it seems a lot of HT anandtecher's are
personally, i can't stand watching some TVs quietly at night because the sounds drive me crazy

 

[SWScorch]

Ack, I too can "hear" Tvs and monitors or the like. Its more like I "feel" the noise rather than "hear" it. I can hear the whine itself, and also can feel the pressure it generates in my ears. I've only met 4 or 5 other people who can hear it. And, what a coincidence, I listen to metal!

 

[454Casull]

I can hear the whine of TVs and monitors too. It doesn't really bother me though.

 

[spidey07]

get your hearing tested. The 20-20K is just a ballpark figure. But given the specs of your system...sounds normal.

Yes, I too hear TVs and monitors whine...people around me say "what are you talking about, I can't hear it".

My anser is B. and you don't have 20-20K hearing.

 

[bizmark]

I can hear the TV noise too. The crappier the TV, the worse it is. My 19" GE POS is almost unbearable most of the time. I can hardly hear my dad's 36" Wega, but still every time I walk in the house I can tell whether the TV's on. Most people that I know can hear it too when I point it out to them.

I did a quick search and couldn't find anything solid on exactly how high-pitched this TV noise is. One person claimed that it had something to do with the 30fps*500 scan lines resulting in a frequency of 15kHz. They may have been using another TV standard, though (PAL?). Can anybody sort this out? I know we've got a few TV tech people here... what component of a TV makes this noise?

 

[Peter]

It's the horizontal flyback transformer, oscillating a 20 kV sawtooth waveform at 15.something kHz (the .something depends on
the format - NTSC is 15.75 and PAL is 15.625 IIRC).

 

[Elledan]

<< Ack, I too can "hear" Tvs and monitors or the like. Its more like I "feel" the noise rather than "hear" it. I can hear the whine itself, and also can feel the pressure it generates in my ears. I've only met 4 or 5 other people who can hear it. And, what a coincidence, I listen to metal! >>


But now the big question: do those people who can hear it too listen to Metal as well?

 

[Elledan]

<< It's the horizontal flyback transformer, oscillating a 20 kV sawtooth waveform at 15.something kHz (the .something depends on
the format - NTSC is 15.75 and PAL is 15.625 IIRC). >>


So that explains why most people can hear the sound generated by a TV. 15 kHz is low enough to be heard by them.

BTW, I just noticed that my the system right next to me (the PSU?) is making some noise as well. I've always been able to hear it, but I just got used to it, I guess =)

 

[Jerboy]

<< It's the horizontal flyback transformer, oscillating a 20 kV sawtooth waveform at 15.something kHz (the .something depends on
the format - NTSC is 15.75 and PAL is 15.625 IIRC). >>




Probing around my TV with a coil, my frequency counter reported magnetic field in 15ish KHz range and 45ish KHz range and I'm assuming latter is from switching regulator within the TV.

 

[im2smrt4u]

<< Elledan - You too? Damn tvs and crappy monitors piss me off. It annoys and even hurts, depending on how pitched it is. And I listen to Metal too. Must be some link there..... >>



Same here, I can tell when a TV is on virtually anywhere in my house, and my old monitor really bugged me because it would whine anytime it was on. I can hear almost anything with a large transformer in it...for some reason it seems like they make a lot of noise...anyone know why that is? Are they really making a high pitched noise?