Is 4kHz too high a beeper frequency?

Listening to a 1 kHz tone I realize that it sounds a lot higher pitch than I would expect. It's still high enough to be annoying, but much less so than 4 kHz and I think it would stand out in the crowd of device beeps.

It just so happens that I designed a piezo-based alarm system last week but haven't tested it yet. It uses a 2kHz beeper switched on/off at ~15Hz to produce a warbling effect. This in turn pulses at 0.5Hz, that is, 1 sec on, 1 sec off. I expect that this will be better at drawing attention than a continuous beep.

Something like that will also be much easier to localise than a constant tone. A lot of trucks in the UK have a reversing noise which consists of bursts of "random" noise in order to make localisation easier.

John

constant

Not to mention emergency vehicles' "sirens"...

Mike.

Indeed. Lots of data here:

John

The standard smoke alarm frequency is 3100Hz.

It's important that the alarm should wake most people, including partly deaf ones. So that frequency is a good bet.

Clifford Heath

When I am testing my smoke detectors I can barely hear the beep, even when I am standing right under it. I strongly suggest a frequency lower than 2 kHz. My smoke detectors have a vocal alarm also.

Bill

I can't hear the standard smoke alarm beeps.

Bill

Bill Gill wrote in news:r7k7f4$571$ snipped-for-privacy@dont-email.me:

WTF are you guys old and decrepit?

Maybe a smoke alarm should hook into one's stereo system and when it goes off, it plays a recording of a fireman pounding on your front door hollering.

Tired of that thump, thump, thump of "Hey buddy you are about to burn to death". Get Billy Rooter! Run Billy... Run Billy...

It's also useful if the alarm can be located when the low battery warning makes it sound for a fraction of a second every five minutes.

I have an open balcony and a smoke detector on that level as well as one right below. On top of that I found out when you remove the battery there is a hold up circuit that makes it continue to beep that way for quite some time. Insane!

Have you thought of asking the health care people who would likely be using this tool what sort of notification they want?

In many cases there are a great many devices beeping and booping all around them, so if this is a life-saving device I would perhaps want to have it also strobe some sort of light to really catch one's attention in a possibly noisy environment.

John

Nice link, thanks.

Yes. The 1 and 2kHz versions have rather large diameters, but thin piezo disk versions can easily slip on top of the circuit board, if tall parts, like inductors, etc., are located elsewhere.

You can also try driving the smaller piezo off-resonance. It'll still put out, just at lower level.

Cheers, James Arthur

Or lower its resonance by acoustic or mechanical coupling. This can also increase the sound output by using a larger surface to couple the sound to the air or an acoustic cavity.

This is what they do in speaker cabinets to improve the frequency response.

My hearing tails off at about 9kHz.

I have a digital thermometer with an approximate 4kHz beeper. I can hear it, but the sound very easily gets 'lost' in ambient noise and I find I have to actively listen for it.

Another thermometer (hers) uses a lower frequency and much easier to hear. Same button cell, so probably similar drive.

John Woodgate would likely be an expert in this, but I don't know if he's still around.

My job takes me into Operating Rooms. And now that you mention it, although ECG beeps are distinctly heard when a patient's first anesthetized, its hard for me to recall if the ECG beeps persist and fade into background noise or if they stop altogether. My attention's usually focused elsewhere. And some surgeons play music during procedures. None of which helps me hear any ECG beeps that may be present.

There was an interesting case of a church office with weird warbling which was hard to isolate. Two phone guys examined their system and came up empty handed. Then the younger of the two used a smartphone app that matched the warble to a similar sound in an online database to identify its source. It turns out that an old medical device was replaced, set aside, and forgotten. Eventually its batteries ran low and it warbled for replacements.

Then there's that horrific clarion of a battery backup in need of service. That gets under my skin, guaranteed, every time.

You certainly must hear some unusual sounds that emanate from coin-op arcade machines.

Thank you,

My job takes me into Operating Rooms. And now that you mention it, although ECG beeps are distinctly heard when a patient's first anesthetized, its hard for me to recall if the ECG beeps persist and fade into background noise or if they stop altogether. My attention's usually focused elsewhere. And some surgeons play music during procedures. None of which helps me hear any ECG beeps that may be present. Upon further reflection, the ECG beeps are always present. When you clearly hear them over the phone you psychologically brace yourself for OR troubles. It's interesting though, how they tend to fade into the background when you're onsite in an OR.

There was an interesting case of a church office with weird warbling which was hard to isolate. Two phone guys examined their system and came up empty handed. Then the younger of the two used a smartphone app that matched the warble to a similar sound in an online database to identify its source. It turns out that an old medical device was replaced, set aside, and forgotten. Eventually its batteries ran low and it warbled for replacements.

Then there's that horrific clarion of a battery backup in need of service. That gets under my skin, guaranteed, every time.

You certainly must hear some unusual sounds that emanate from coin-op arcade machines.

Thank you,

Sheesh! Last night at 2 am one of our Kidde smoke alarms started honking loudly twice every 30 seconds. I stumbled around in the dark, trying to find the one was responsible. Figured it was beeping for a new 9V battery, once a year, even though they run on 120Vac - ggrrr! They all showed a tell-tale green light, saying I'm OK. But I was looking at one when it beeped, and saw a red LED flash. Turned out it was a combo smoke/CO unit, claiming end-of-life, 10 years, even though it was only 7 years old. Gggrrr!! Rotate it off the bracket, pull out the power plug, get it down, and remove the battery. Sheesh! finally, some peace and quiet. Calm down, back to bed. Damn those Kidde engineers.