Is 4kHz too high a beeper frequency?

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** Yes, it is the ear's most sensitive frequency.

However it's also the most easily damaged by exposure to high SPLs so the first to go.

There are a number of reasons for picking a high frequency - including the inherent echo in most rooms with bare walls. Frequencies in the range of 2 to 4kHz do bounce around a lot.

.... Phil

hil

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** I am astonished too - seems there are lots of 80 & 90 year olds lurking here - many with SEVERE hearing loss.

I am 67 and find the sound of my smoke alarm *painfully* loud - and it needs to be to WAKE you up.

FYI:

I can easily hear 10kHz.

My threshold at 4kHz is about 30dB SPL rising to 50dB SPL at 10kHz.

Checked today with a known good meter.

.... Phil

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** There are links to John dated 2015 for recent a publication of his on hearing aid loops.

.... Phil

Unscientific test using plastic/mylar cone speakers: 1 inch dia: 3.8KC peak loudness, 4.0KC limit. 2.25 inch dia: 2.5KC, "useful" to 3.2KC, reasonable sound to 4KC, still there at 8KC (broad "peak" 7KC-9KC).

Do not know my hearing top-end is on above tests; ost likely below the 15KC TV. After all, i am only over 80 (what is this about 45?).

Robert, everyone's different. It's just a general rule that top end hearing declines with age and there may be odd rare exceptions to that rule. If you're one of them, just be grateful!

Our (UK) jazz supremo the late Humphrey Lyttelton (and humorist, writer, broadcaster, cartoonist, calligrapher, etc etc) said, on learning that rule, that he could hardly wait!

Mike.

• Winfield Hill :

Of course there will be people who don't hear it.

Our oven timer has a beep at g'''' (G7, 3135 Hz), and the volume is adjustable in three steps. I can hear it at the highest volume setting when I'm in the same room, but not when I'm in the next room, even when the door is open or ajar. My sons then shout from upstairs "Pa! It's beeping! It's ear-splitting!"

Our Braun Thermoscan ear thermometer beeps at h'''' (b7, 3950 Hz) when the measurement is finished. Of course, it's a faint beep, because the device is only some 10 cm away from the ear measured and about 30 cm from the other. I don't hear it; luckily, there is also a LED that signals the end, so I measure my body temperature in front of a mirror.

I'm 63 and I don't have a hearing aid (probably should have one).

- Andi

Yes there are many people who cannot hear the beeper in a smoke detector. They make smoke detectors with a voice alarm and that is what I have.

Bill

Bill Gill wrote in news:r7mr8r$bb4$ snipped-for-privacy@dont-email.me:

I'd pump it through my stereo... or get a nice 'tick box' (shocker) and 'connect' (to myself) that when I lay down to sleep. Guaranteed to wake you faster than a smoke alarm. It is essentially a single, hot tick from a tazer driver (toned down a bit). All depends on where you decide to attach it.

It says WAKE UP! to wherever you decide to 'attach' it. Hook it to your alarm clock or your smoke alarm. Do not hook it to your nuts.

Having trouble getting that dumb 30 year old child of yours out of the house? Get him "up for work" using this a couple times! Use the 'multiple-tick' setting. Definitely *near* the groin. He'll move out real quick.

Thinking of other means or have a bad rodent problem? Use it to light off your rodent eradication explosive devices.

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** You have a serious hearing loss, maybe due to exposure to loud noise for years. Get it checked out soon.

..... Phil

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** Only those with severe hearing loss.

** Good.

Most kids up to age 13 are not woken by regular smoke alarms, even in the same room and need an alarm like yours. A completely different issue though.

.... Phil

If you are competing with other enunciates, why not something unique, Three descending tones 3k 2.5k and 2k and repeat. Or the same, plus a ramping freq back up from 2k to 3k, then repeat.

Mikek

Right. Lower resonance means large transducer but the ear is not as sensitive here so higher power too, to have the same loudness as a higher frequency... But not TOO high of frequency.

Also, larger diaphragm or transducer usually means more mass so higher power. This is one reason that sub-woofes require more power than the mid and high satellite speakers.

Good old Phil from Australia would even know this but I have him kill filed so hopefully wouldn't see his response except through someone copying.

Yeah... Square wave or something with harmonics would help too.

booB strikes again !!

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** Utter bollocks.

The increased moving area *more* than compensate for the extra mass.

** Oh dear - "wall to wall thinking" when one mistake generates a host of of others to back it up.

The "sensitivity" of woofers is much the same as for mids and tweeters.

Typical numbers are around 90dB /watt /metre in each case.

** Well no.

I do not know this cos it ain't true.

Who would ever believe a Boob, anyway ?

..... Phil

That depends entirely on the details. A piezo chirper has very poor coupling to the air. The acoustic or mechanical coupling can be done in a way that makes the coupling more efficient giving more volume for the same power.

Doesn't matter. Win has given no indication of being interested in designing a speaker cabinet. He obviously is more comfortable with electronic design.

I'll likely be the brunt of his missive and I will be replying if he does, so you can read all about it if you wish.

--

  Rick C. 

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I have dismantled a few smoke alarms. The piezo disc has a resonant cavity behind it and a small horn in front, so they have made an effort to maximise efficiency for a small range of frequencies.

John

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** The electro acoustic efficiency of a piezo transducer is very high providing the diameter is about 1/4 or more the wavelength.

FYI: 4kHz has a wavelength of 84mm so 1/4 = 21mm.

They present a capacitive load of a few nF to the source with a small resistive component.

.... Phil

Don't tell me. Tell Win. He is the one building the device.

I was talking about coupling the piezo to a larger mass and surface to lower the resonant frequency of a small piezo and at the same time increase the efficiency. I wasn't criticizing any product.

--

  Rick C. 

  -++ Get 1,000 miles of free Supercharging 
  -++ Tesla referral code - https://ts.la/richard11209