cautionary BBD tale

[loss1234]

I have hurt my ears very badly. I dont know how long it will last. I hope only a few days. But the RINGING is worse than any I have ever experienced.

And it all happened because of BBD's. (mn3207 and Mn3201)

here is what happened.

I was trying to build a simple circuit following the zombie chorus and also the Datasheet echo circuit.

I wasnt hearing anything at all. I was getting a little bit of guitar at some points, but at others just a faint high pitch (clock?)

but no chorus.

this went on for a long time, with me moving the trimmer, etc.

And when i looked at the VU meter on my audio interface, i saw it was MAXED!!

uh-oh

turns out I was hearing really loud SUPER HIGH FREQUENCIES either caused by oscillations or by the clock

now, a day later my ears are still very bad.

and no working circuit


i only hope the MN3207 zombie chorus schematic is error free because I would hate to think I damaged my ears chasing something that doesnt work!

most likely I screwed up. Just not sure how.


the thing is, I cant figure out how to do the trimming WITHOUT the sound on.

any advice on how to avoid this problem in the future and get a working BBD circuit?

thanks

[Taylor]

I don't know a ton about BBDs, so offhand I don't know what the clock frequency was, but I think they are usually around 100khz. You've probably heard before that people can only hear from 20hz-20khz, but in fact most people can't hear past 16k or sometimes 18k, far below the clock frequency. If you can't hear it, it's not going to do much damage to your ears.

Secondly, you didn't mention what you were listening through, but assuming it's a  guitar amp and cab, these things do not have response that high. Most guitar cabs go way down in sensitivity by 10k. They certainly can't reproduce 100k with any power.

I don't know why your ears hurt (psychosomatic?) but I don't think the BBD did it.

[Ripthorn]

Oscilloscope, maybe?

[loss1234]

no it was definitely audible. just not so much that i thought it was loud. 

lesson learned.

my only point was that I really really hurt my ears.

they have been screwed to the point of almost going to the doctor.

i think i messed something up with the 4046 as it was putting a lot of clock noise into the ground.


oh well

[loss1234]

as far as the scope goes...does anyone know WHAT i should be looking for with the scope on the BBD in and out trimmers?



and if i use the mn3102, are its clocks easily visible on the scope or are they too high freq?

sorry for sounding like an idiot. (i have never found any area of DIY so hard as BBD's)

[Taylor]

I don't know, I still don't really think that's what happened.

Have you ever watched television? Televisions put out high pitched sounds right around the upper bound of human hearing. All the time. Even when muted. If you have ever watched TV, or even been in the same room as one, you have heard prolonged high frequencies at an audible volume.

But anyway, to answer your question about how to test without hearing it, wear some ear muffs. I got a pair at Harbor Freight for cheap.

[loss1234]

I appreciate your advice but I know when i have simply heard a high pitch noise from a TV and when i have hurt my ears.
what I keep pointing out is that

1. my soundcard and speakers CAN and do go up to 20khz

2. i had screwed up the PLL circuit somehow so it was bleeding into the outs. in fact today, hoping to fix the circuit, i kept the soundcard volume at zero, and turned the circuit on. sure enough, the  inputs on the preamp were maxed and when i turned the volume up just a little bit i heard a high pitch whine.

i was only able to get it to stop by killing the PLL output 100k from pin 12 off the 4046.


my only point with this thread was that I had never worked on a circuit that put out such a bad whine when connected wrong or mis-trimmed.

(the zombie chorus MN3207 version)

i dont think this reflects poorly on the schematic but on my build.

i was just trying to relate my negative experience.

thanks

[aziltz]

i hope you recover quickly and fully.

I tend to turn up the guitar a bit too loud when I'm in "the Zone" and my left ear can get a little funny at concerts now.

[loss1234]

thanks man!!

yeah my right ear is near shot from years and years of playing in bands without ear plugs....didnt start till it was far too late.

[Cliff Schecht]

Prolonged exposure to sounds at elevated levels for a sustained period of time WILL damage your hearing. Higher frequency signals can carry more power than an equal amplitude low frequency signal (higher frequencies/shorter wavelengths propagate easier through air) and thus can do a lot of damage to your hearing. If you were listening through your computer speakers at enough volume then I can believe that you did hurt your hearing. If the pain doesn't go away, you will want to go see a doctor about the situation. Be more careful of your hearing in the future, the damage you do to your ears is cumulative and can't be reversed (without stem cells at least).

Something that I've always enjoyed doing in the lab is to take a function generator and set it right above the threshold of human hearing (21-24 kHz works well). Play this tone through a speaker or PA and almost instantly, you'll start to feel uneasy and get a headache (not the funny part). The funny part is watching everyone else in the lab start to feel like crap and have no idea why . Not the nicest thing to do though, so make sure to not piss off any strangers!

[JKowalski]

Prolonged exposure to sounds at elevated levels for a sustained period of time WILL damage your hearing. Higher frequency signals can carry more power than an equal amplitude low frequency signal (higher frequencies/shorter wavelengths propagate easier through air) and thus can do a lot of damage to your hearing. If you were listening through your computer speakers at enough volume then I can believe that you did hurt your hearing. If the pain doesn't go away, you will want to go see a doctor about the situation. Be more careful of your hearing in the future, the damage you do to your ears is cumulative and can't be reversed (without stem cells at least).

Something that I've always enjoyed doing in the lab is to take a function generator and set it right above the threshold of human hearing (21-24 kHz works well). Play this tone through a speaker or PA and almost instantly, you'll start to feel uneasy and get a headache (not the funny part). The funny part is watching everyone else in the lab start to feel like crap and have no idea why . Not the nicest thing to do though, so make sure to not piss off any strangers!

There are some kids in my high school who are obsessed with downloading soundclips of high frequency signals to their cell phones and playing them in class... The teacher's can't hear it, typically, as they are older, but I can hear it perfectly. So ridiculously annoying. And it's pretty hard to pinpoint the source....

And then we also have CRT TV's that are on all day for announcements and scrolling notices, and I can hear those perfectly to. They are surprisingly loud, actually.

It all really helps with my concentration 

[Mark Hammer]

Your ears are built such that high frequencies are detected principally near the entrance to the cochlea.  This is presumably because a) lower frequencies are longer wavelengths and presumably result in peaks further along the cochlea, and b) because the sound is being transmitted through fluid, losing energy as it travels.  Since most high-frequency content in nature is lower amplitude, evolution made our ears such that we detect high-frequency content before it runs out of energy to BE detectable.

But the thing to keep in mind is that there is a difference between conscious detectability, and the physical response of the sensory system doing the detecting.  You know how you walk around outside on a sunny winter day, and you come inside only to feel like you've just been blinded?  There's a case of a sensory system being overloaded in a way that is not consciously detectable in that context, but rears its ugly head in a different one.  So it IS possible to be exposed to something that does not seem robust enough to attract anyone's attention, yet can do damage or at least temporary scrambling.  And as you know, the human auditory system is most sensitive (at least in terms of conscious detectability) to those frequencies in the range of the human voice, with higher and lower frequencies being audible, but needing to be much greater amplitude to be equally audible.

Although the brunt of us these days are not spending much time in front of screens that have flyback transformers whining away at 15.75khz (the tradition "whine" of a crt TV), many can probably remember having headaches after periods of extended viewing that didn't seem to have an explanation.  They were from being blasted with a 15.75khz tone that was not "loud enough to notice" but was loud enough to cause temporary trauma to the auditory system.

So loss1234 is not imagining anything.  Well, let me correct that.  He was imagining it was quieter than it really was.

Since the exposure was prolonged but not chronic, one would expect the same consequences as any short-term insult to the body.  So you should probably expect headaches and hearing "issues" for a few days, but it should clear up, the same way that one's ears would be ringing for several days after a loud concert, and clear up by a week's time.  Of course, the same happy ending would not be the case if the exposure was chronic.

It's unfortunate it happened, but lucky you caught it and were generous enough to draw it to our collective attention.

So, get well quick, and thanks.

[Top Top]

There is a house near mine where there is some sort of high frequency sound generator, just near the threshold of audibility but very loud.

It is really obnoxious when you walk past it, makes you feel dizzy. I don't know if it is supposed to scare away some kind of animal or perhaps teenagers 

[aziltz]

they use those kinds of things to get ride of ground burrowing rodents and animals.