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highly selective filter

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Thunderchild

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I need to make a band pass filter perhaps a single low pass or high pass will do but to be certain I want to centre around the human voice range (what is it btw ?) i was thinking thhe op amp with the two Rs and Cs but is there something even more selective like using inductances ? what formula do u use in a RL filter and what is thhe schematic ?
 
Thunderchild said:
I need to make a band pass filter perhaps a single low pass or high pass will do but to be certain I want to centre around the human voice range (what is it btw ?) i was thinking thhe op amp with the two Rs and Cs but is there something even more selective like using inductances ? what formula do u use in a RL filter and what is thhe schematic ?

Opamp RC filters are all you need, there are plenty of examples of voice bandwidth filters - about 300Hz to 3KHz is about right.
 
well this is the problem. I work on offset printing presses that are quite noisy. so I want to wear protective headphones. inside these I want to wear headphones (the small ones that go in your ear) into which I want to feed a highly filtered signal from a microphone so I can still hear people speking to me.

ps I meant LC filter above not RL
 
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Thunderchild said:
well this is the problem. I work on offset printing presses that are quite noisy. so I want to wear protective headphones. inside these I want to wear headphones (the small ones that go in your ear) into which I want to feed a highly filtered signal from a microphone so I can still hear people speking to me.

ps I meant LC filter above not RL

That would be difficult, as printing presses and the like have wide bandwidths of noise, and these bands would cover the range of human speech. Telephone systems work well with speech, and they are <4KHz BW. Using such a filter would pass human speech, but a lot of the noise as well.
 
hm yea sounds like I need a new job my main problem is actually low frequency and probably subsonic as heavy paer is printed at like 1.6 sheets a second but what causes me problems is that sound pressure cause by the flaping of thhat heavy paper it is a bit like going up in a pllane sometimes
 
It has been my experience that low frequency noise affects the body more than the ears, perhaps a "space suit" (something that keeps your body under constant pressure) would aleviate the problem.
 
A few things:

A. I've seen, in amateur radio publications, some detailed information on the frequencies where most of the information in spoken words resides. Contact me directly if you can't find that stuff.

B. Can you obtain data on the characteristics of the noise in your area? You might find that you can suppress the energy without affecting the voice frequencies.

C. Have you looked at noise cancelling circuits or devices?

Sounds like an interesting project.
 
Loud sounds can damage your hearing and infrasound can be a health hazard. You shouldn't be around noisy machinery without ear protection and there might also exposure limits for infrasound exposure too. Your location say Italy which is in the EU so you should be protevted by EU health and safety laws.
 
safety laws in Italy haha yea I bet there are a few but there is another law thhat won't found in the constitution but in evvery persons mind: laws are made to break !
I think it is not a health threatning intensity but the long exposure does make me even more tired. I have got a pait of ear mufs and they seem to do a pretty good job. main problem is I suffer from tinitus (ringing in the ear) and thhat is worsend by loud noises and stress, I have both at work.
 
Go and see a doctor, if you can prove your tinitus is work related then you might be entitled to compensation.

Have you had any other health problems while working with that particular machine? If so they might be related to infrasound exposure, or (more likely) hazardious chemicals used/released by the procedure.
 
How about keeping a note pad & pen handy? Anyone needing to talk to you while you are working will just have to write a message.

If you are going to undertake a filtering project, I bet others at the same place have the same problem. Why dont you get your company to pay for your efforts in solving their problem. ;)
 
I need to make a band pass filter perhaps a single low pass or high pass will do but to be certain I want to centre around the human voice range (what is it btw ?) i was thinking thhe op amp with the two Rs and Cs but is there something even more selective like using inductances ? what formula do u use in a RL filter and what is thhe schematic ?[/QUOTE said:
human voice b/w overall is 20hz to 20 khz but u can reduce according to application,
plz conform
also u can make band pass filter w/o inductors using higher order filters or elliptical and chebshev responses.
wt is the attenuation and cut off freq requirements ,
 
well as for compensation haha, I have always had tinitus but I don't think a doctor (and mine happens to be a client of the firm so you go figure) can evaluate exactly to what exstent the stress I am under due to chaos caused by total disorganisation of my boss (an ex priest so you go figure) who just wants more and more work and perfect results from machines he will not keep proporley maintaned.
Italy is not a country for people fighting foe their rights and is is a small company only two presses that print one colour at a time they are 35*50 and 50*70 cm paper size but still are noisy and as I say a 50*70 cm sheet of 300 g/m2 paper can make quite a disturbance an it seems that I am the only real sufferer or the other don't realize what it might do to them probably on a much smaller scale as it just seems I am affected by this god knows what I would be like near the huge presses used industrially. the headphones I got make a lot of difference and I can still here people they just have to put up with the fact that they recon I can't hear them when actually I can hear them better because higher and lower frequenzys are filtered out better letting me hear more of what people say anyway. else I just take them off for a moment. I plan leaving soon anyhow so not much point making a deal of it I think it is just that I am more sensitive than others and it is not recomendable that I do a noisy job. the others think I am nuts or prefer to pretent so because they don't want to stick out. well the headphones have made a difference and despite the sarcasm of my boss I will wear them when I feel like it, but thannks for all your suggestions people
 
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