Why are many devices designed with very high pitch buzzers  - Page 1
Forum section: electronics / general

author: Back2Volts
author_rank: Unknown
timestamp: February 05, 2018, 04:27:27 am
content: I am high there on age, and my hearing on the high audible end is almost gone. Because of this, I have come to notice that there are many devices out there that have been designed with audible signalling that makes use of a very high pitch sound, at very low levels. The combination makes them inaudible for me.For example, I am down with the flu... I cannot hear the thermometer beeping "done".The Kenmore refrigerator beeps when door left open... could stay all night. (Replacing all kitchen with Kenmore was our big mistake)My wife bought some lost-key locator gadgets, supposed to beep to draw attention to lost item... Got a few for Christmas gifts. Unusable... even for my wife that has no problem.It seems to me there could be better design choices.At times it has crossed my mind that I could use a pitch-translating-buzzer for the refrigerator. Something small, permanently plugged on kitchen outlet, or on USB. Also, may be an iPhone App for cases where I am waiting for the beep.

author: BrianHG
author_rank: Super Contributor
timestamp: February 05, 2018, 04:51:15 am
content: Price, size, and power drive requirements. The ceramic tweeters, or ceramic transducers make that much audible noise without any amplifier or speaker cabinet. They are driven without an amplifier with only a few ma cycling at the right frequency coming out of a MCU's IO pin. If you were to use a normal speaker, you would need an audio power amplifier to make any good volume of audible sound at all. Especially if you have a watch battery powered device, or a tiny enclosure where the transducer can only be engineered efficiently to higher frequencies.Poor choice of transducer, or drive frequency, or, poor placement in the device may make the volume lower than what these transducers can truly produce, but, these devices are multitudes more efficient than a normal magnet with coil driven as in a normal speaker.In fact, they can be irritating to our ears and this may be why the volume is kept low. But, it the device is small, they must use the higher pitch as it will be the operating resonant frequency of the cheapest possible device.

author: phil from seattle
author_rank: Super Contributor
timestamp: February 05, 2018, 06:07:01 am
content: That's my complaint as well. Even with hearing aids, I can not hear a number of those devices. On my sub-zero fridge all the door alarms are inaudible to me. For an expensive unit, you think they could have splurged another $0.50.

author: BrianHG
author_rank: Super Contributor
timestamp: February 05, 2018, 06:11:38 am
content: Quote from: phil from seattle on February 05, 2018, 06:07:01 amYes, I know. But, this is modern life. $0.50, but not just that, the additional $0.20 for a buffer amp, the additional mechanical quality placement area, over millions of units sold means someone is lining their pockets with that $$$, and I bet it's not the engineer who was told to make it that cheap is seeing a cent of it...

author: phil from seattle
author_rank: Super Contributor
timestamp: February 05, 2018, 06:15:23 am
content: I'm not convinced it's such a huge cost item. Wonder what an ADA lawsuit would do to them.

author: BrianHG
author_rank: Super Contributor
timestamp: February 05, 2018, 06:21:27 am
content: The engineers are being told to keep it as cheap as possible. The engineers are just trying to keep their jobs...We are not talking about a fancy 10K$ sound system here.

author: phil from seattle
author_rank: Super Contributor
timestamp: February 05, 2018, 06:43:06 am
content: Yeah, not $10K sound system. But my fridge was something like $5K to put it in perspective. So, do you think they did the right thing?

author: Jeroen3
author_rank: Super Contributor
timestamp: February 05, 2018, 06:45:21 am
content: You can't hear a 4 KHz beep?

author: jh15
author_rank: Frequent Contributor
timestamp: February 05, 2018, 07:20:11 am
content: Need to require a wheelchair ramp for the ears. Sue them!

author: BrianHG
author_rank: Super Contributor
timestamp: February 05, 2018, 07:36:42 am
content: Quote from: phil from seattle on February 05, 2018, 06:43:06 amIt's more like I think it isn't affecting the product's primary function, being a fridge...You are right, and I agree, some of these minor useful features within said products could be better though-out, tested under real-world circumstances and better engineered, but the OP's question was why were weak high pitch sounds being used & I gave the answer.

author: james_s
author_rank: Super Contributor
timestamp: February 05, 2018, 07:46:00 am
content: An engineer who "needlessly" (according to the bean counters) adds 50c to the cost of manufacturing something sold in huge quantities is going to risk being unemployed. When you work in a corporate environment it's not uncommon for stupid things to be mandated by someone in upper management who is justifying their own job.

author: nessatse
author_rank: Regular Contributor
timestamp: February 05, 2018, 07:47:37 am
content: So happy someone brought up this topic. I am basically deaf to anything over 2kHz and my biggest gripe is with multimeter continuity testers which mostly seem to run at around 2kHz. Hearing aids (at least mine) don't help much because they seem to confuse the tone with audio feedback and turn down the gain. It would be really nice their was a meter with configurable continuity tones

author: BrianHG
author_rank: Super Contributor
timestamp: February 05, 2018, 07:57:33 am
content: Quote from: nessatse on February 05, 2018, 07:47:37 amCheck if the firmware for Dave's meter is available, maybe you can edit it to play a 1.5 KHz tone. You may need to change the transducer, or, add signal current to it to hike up the volume.I personally would add a 1w high efficiency white led driven by a mosfet on the IO driving the transducer making a GIGANTIC visual queue for those hard of hearing which you wouldn't miss even if you are not even looking in the same direction as the meter...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 05, 2018, 08:11:13 am
content: On a related note (ha), frequencies 2-4kHz are the least directional to human ears. So, it's high pitched to begin with, and you also can't tell where it's coming from. Great!And yeah, piezo disks are mechanically resonant at some kHz, depending on size. Smaller size = cheaper, what do you expect.On the upside, I can still hear 15.7kHz, so that's nice... (I suppose most of the posters here were, well, a little more careless in their younger days regarding loud noises -- or are just predisposed to hearing loss.)Tim

author: Zero999
author_rank: Super Contributor
timestamp: February 05, 2018, 10:39:28 am
content: I find the high pitched beeping noise annoying.I wonder how difficult it would be to add a frequency divider, a couple of booster transistors and a small speaker. I suppose it depends on the device, what sort of power supply it uses and whether there's room to fit a speaker.

author: TheWelly888
author_rank: Frequent Contributor
timestamp: February 05, 2018, 10:56:19 am
content: I hate those high pitch buzzers - I call them "Cheap Beeps"! When I was wearing hearing aids so many devices had them, eg a wall phone with a high pitch ring tone and the Fluke continuity beeper. I resented the exclusion just because I could not hear them.I was lucky that I got a cochlear implant which gave me the ability to hear high pitch sounds and these are now accessible to me. Having said that, I really do not like these cheap beeps fitted to devices and believe that any device with a tone should have some kind of visual indication that it is sounding and use a tone of no higher that 2kHz.

author: StillTrying
author_rank: Super Contributor
timestamp: February 05, 2018, 01:43:38 pm
content: Quote from: T3sl4co1l on February 05, 2018, 08:11:13 amAfter years of hearing 15.625kHz, I'm down to 14.7kHz now.

author: Back2Volts
author_rank: Unknown
timestamp: February 05, 2018, 03:00:41 pm
content: Quote from: Jeroen3 on February 05, 2018, 06:45:21 amHave no way to determine if it is 4 Khz or not. All I can say is I cannot hear the beep, but on the other hand, I can hear you sound surprised, like it was my fault.

author: Tom45
author_rank: Frequent Contributor
timestamp: February 05, 2018, 04:10:20 pm
content: Long ago I could hear the 15.7 K TV horizontal oscillator. Now I wear hearing aids. And there are no longer TV sets with 15.7 K to listen to anyway.A funny story. A few years ago I used an unfamiliar meter to test some wiring continuity. I couldn't hear the beep. Not that unusual for me and I blamed my ears. But even if I placed the meter next to my ear, I couldn't hear it. Turned out that meter's default was to not beep. No problem hearing it once I turned on the continuity beep.

author: sokoloff
author_rank: Super Contributor
timestamp: February 05, 2018, 04:25:57 pm
content: Quote from: Back2Volts on February 05, 2018, 03:00:41 pmTone conveys poorly over text (pun not originally intended, but I admit it does please me...)I wouldn't assume Jeroen was assigning fault/blame, but merely surprise. To me, 4kHz was much lower than I expected frequency-dependent hearing loss to have progressed as well. (IOW, I could have easily asked the same question, because I was thinking it.)

author: Bassman59
author_rank: Super Contributor
timestamp: February 05, 2018, 04:40:06 pm
content: Quote from: Hero999 on February 05, 2018, 10:39:28 amIt'ssupposedto be annoying. It's intended to get you to close the refrigerator door!

author: Jeroen3
author_rank: Super Contributor
timestamp: February 05, 2018, 04:43:36 pm
content: Yes I am surprised. Since not being able to hear 4 KHz is like always listening trough a phone.I’m just 25, with very slight tinnitus. I always wear protection.Good thing you mention this. Now we can put this on the list of things for best accesibility. (Next to color blindness, which is often forgotten)

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: February 05, 2018, 04:45:22 pm
content: I have a friend who got a brand new Fluke this past Christmas. So I was doing continuity checks to show him how it's done. I must have done like 50 or so such checks when he asked the question "how am I doing that without looking at the meter". It was then I discovered he couldn't hear it.Even with the bloody thing up to any ear it was silent.I agree with you on the piezo thing. Make it with the ability to be pitch shifted or the ability to change the loudness, especially with a menu driven system.Get Atty. Jim Sokolove (US ambulance chaser) to do a mass lawsuit on it... If he's not too busy with Meso...On a similar story set in a time looooooog ago, I was a young man and was just starting out at the local TV repair shop in town.There was this service call, and my very nice old, but sickly boss was not one for hanging around in a customer's house for too long.So in my rush to get in and out, I adjusted, "twiddled" the slug tuned type horizontal frequency control.I was doing this from behind the set without looking at the screen. I heard the thing going into lock.I exclaimed there you go, all set. It confounded him.I explained how, and he asked how I could have heard such a thing. In my ignorance I asked "how can't you"?I'm now approaching his age, but thankfully I can still hear up at 15,750KHz.Such stupid question to have asked in my youth...

author: Electroplated
author_rank: Regular Contributor
timestamp: February 05, 2018, 04:51:06 pm
content: I've recently had an interesting experience with high pitched sounders when I made a dual freezer alarm with an Atmega.Its has two '1 wire' sensors that display the actual temperature, once either go above a trigger point an LED lights for each sensor and an alarm is triggered, it works but setting the alarm tone was 'fun'The first frequency I chose was OK for me but too loud for my daughter ( hit her sweet spot) and it annoyed my wife. the next frequency I tried was OK for me and the daughter but my wife told me it sounded like the monoxide alarm, next one tested I could hardly hear it but everyone else could.Eventually I ended up using an old two tone sounder I had in stock, but not before annoying the dog and cats. The only thing with the two tone sounder is its too loud, so I was told so had to mute it a little with tape over the hole, sigh..........

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 05, 2018, 06:59:33 pm
content: Anything using a piezo needs to be tuned to the resonant peaks of the transducer/cavity combination to get a decent output. There are often 2 or 3 useable peaks, and audibility can often be improved by chirping or hopping between these peaks, and the chirping can also generate lower-frequency components that may help audibilty.But they're always going to be fairly high as lower pitch needs a physically bigger transducer and cavity, which there is rarely room for.

author: TheSteve
author_rank: Unknown
timestamp: February 05, 2018, 08:50:55 pm
content: Quote from: nessatse on February 05, 2018, 07:47:37 amMy Keysight U1282A let's me select from several frequencies.edit - it isn't a huge range but they do give quite a few options. It is handy if you have two meters in operation not too far apart.They offer:3200 Hz, 3268 Hz, 3339 Hz, 3413 Hz, 3491 Hz, 3572 Hz,3657 Hz, 3746 Hz, 3840 Hz, 3938 Hz, 4042 Hz, 4151 Hz,4267 Hz

author: james_s
author_rank: Super Contributor
timestamp: February 05, 2018, 09:00:56 pm
content: Quote from: T3sl4co1l on February 05, 2018, 08:11:13 amI thought it was low frequencies that were hard to locate the source? Hence the typical single subwoofer in a stereo system.I can just *barely* hear the 15.7kHz horizontal frequency of standard resolution CRTs now, and only if it's a loud one or I put my ear right up to it. My partner on the other hand is just a few years younger than me and she starts moaning about the awful sound the moment I power on an old monitor on the other side of the room. I still remember in highschool I would astonish one of my teachers by walking into the room and immediately informing her that someone had left one of the monitors on over in the video editing station, I think she thought I was psychic. The monitors made what I remember being an ear piercing whine when they were not fed a video signal.I also occasionally got amusement from repeatedly beeping the continuity tester on multimeters in my applied physics class, the older gentleman teaching the class couldn't hear it at all and spent what seemed like a good deal of time looking quizzically at the kid across the room yelling at me to knock it off. Good times.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 06, 2018, 05:34:37 am
content: Quote from: james_s on February 05, 2018, 09:00:56 pmThat too. Peak directionality is in the vocal range, more or less, then a dip around 3kHz, then it goes back up. 3kHz corresponds to about a wavelength at head-size, so your ears can't sense a phase shift, and diffraction keeps the intensity similar on both sides of your head. At higher frequencies, the ears don't seem to bother with phase, but the shadow is significant.Tim

author: Zero999
author_rank: Super Contributor
timestamp: February 06, 2018, 11:32:00 am
content: Quote from: TheSteve on February 05, 2018, 08:50:55 pmUnfortunately those frequencies are too high for someone who's half deaf.

author: Tom45
author_rank: Frequent Contributor
timestamp: February 06, 2018, 12:39:53 pm
content: Quote from: TheSteve on February 05, 2018, 08:50:55 pmIt never occurred to me to use different frequencies to distinguish between meters. I'll have to do that with my two U1272a meters. Thanks for the idea.

author: Zero999
author_rank: Super Contributor
timestamp: February 06, 2018, 02:43:48 pm
content: Want to turn the tiny beeper sound into a loud buzzer? Try this circuit. Obviously you need room for the speaker and big power supply, so no good for a 'scope or meter, but it might be able to fit in the empty space inside a fridge or microwave. If it's not loud enough, use another driver, connected to the Q' output of the 74HCT74, forming an h-bridge.

author: BrianHG
author_rank: Super Contributor
timestamp: February 06, 2018, 03:01:05 pm
content: Just to make use of the existing buzzer 1/2 frequency and louder, and optional 8 ohm speaker, you can simplify that circuit down to 2 ICs and 2 caps. Also low enough power for volt meter with 1 resistor in the circuit.

author: Maxlor
author_rank: Frequent Contributor
timestamp: February 06, 2018, 05:24:40 pm
content: TheAgilentKeysight U1241B has a configurable beeper as well, settable to 2400Hz, 1200Hz, 600Hz or 300Hz. It's not very loud at 300Hz, but that suits me fine in a quiet lab.

author: sd
author_rank: Unknown
timestamp: February 06, 2018, 05:27:58 pm
content: Quote from: Hero999 on February 06, 2018, 11:32:00 amThe Keysight U1242B lets you select from 300Hz, 600Hz, 1200Hz and 2400Hz.Although my hearing is fine, I find that the buzzer on the U1242B is really anemic compared to other meters. Maybe the unit that I have has a defect.

author: Zero999
author_rank: Super Contributor
timestamp: February 06, 2018, 10:07:14 pm
content: Quote from: BrianHG on February 06, 2018, 03:01:05 pmI don't see how you can make the existing buzzer both half the frequency and louder. If the frequency is halved, the sound output will be reduced, because the sounder won't be big enough, to produce the lower frequency. The only way to make it louder is to use a larger transducer.The discrete driver in my circuit could be replaced with an IC such as the SN754410, but the losses will be higher, as it drops 1.4V on the high side and 1.2V on the low side. It also has a relatively high quiescent current. There's the DRV8829, but discrete BJTs are much cheaper.

author: BrianHG
author_rank: Super Contributor
timestamp: February 06, 2018, 11:19:14 pm
content: Use the 74HC74 to divide the output in half. Use 74HC245, 4 of 8 inputs on Q and the other 4 of 8 on ^Q outputs of the 74HC74. Parallel the 2 banks of 4 on the outputs, use a 10uf np cap in series on one side and you will get the 10vp-p.At 1-2Khz, these buzzer transducers with that 10vp-p will make a sound which will fry your ears even though their peak resonant frequency may be at 4khz. I've driven cheat 4KHz units with a single IO from a PIC and it is deafening with the +/-2.5v (5vp-p), +/-5v (10vp-p) (4x power at a given resistance, but let's assume the buzzer is half efficient at half frequency) of a balanced output, square wave would be heard throughout the house.Being all 74HC, this circuit will idle at no power. 10uf cap is fine for the series resistance of even an 8 ohm load at 2KHz let alone the series resistance of one of those buzzers. Use 100uf if you really need every drop of current.

author: Zero999
author_rank: Super Contributor
timestamp: February 06, 2018, 11:37:30 pm
content: Quote from: BrianHG on February 06, 2018, 11:19:14 pmI'm not convinced.The 74HC245 has a maximum total current through all of the pins, of 70mA, so an 8Ohm speaker is out of the question. You could probably get away with a 64Ohm speaker, assuming the duty cycle isn't 100% and the 74HC245's output resistance will help limit the current to a safe level.If the piezo is driven from an IC with a 5V supply and complementary outputs, which is very common, there will be no power increase from driving it with a 74HC245. If the device has a single ended 3V output, then you will get some power increase by using a 74HCT245, run off 5V, but whether it makes up for the loss in volume, due to the lower frequency, is another matter.

author: BrianHG
author_rank: Super Contributor
timestamp: February 07, 2018, 12:22:26 am
content: Yes, a 2 transistor drive output, even an NPN/PNP common emitter drive from a single 74HC74 will nail an 8 ohm load compared to any CMOS IC, balanced will double it, I cant argue there.

author: Mr. Scram
author_rank: Super Contributor
timestamp: February 07, 2018, 12:22:59 am
content: Quote from: sokoloff on February 05, 2018, 04:25:57 pmMe too. To my mind, 4 KHz is way down there. However, if I look at the numbers, the more senior citizens amongst us can expect significantly reduced hearing in that range too. Normally you wouldn't really suffer from it until you reach a very respectable age, but damage can significantly increase your "ear years".

author: cdev
author_rank: Super Contributor
timestamp: February 07, 2018, 02:13:36 am
content: You can significantly increase the number of years your hearing remains decent by taking antioxidants.Quote from: Mr. Scram on February 07, 2018, 12:22:59 am

author: Red Squirrel
author_rank: Super Contributor
timestamp: February 07, 2018, 03:31:25 pm
content: For me it's the opposite I find these tones can be ear piercing at times. I bought a radio and every time you press a button it beeps loudly in what I assume is around 5khz tone. Thankfully you can turn that off but it's not obvious how and have to pull the manual each time. May need to open it and just remove the buzzer.Imagine in a zombie situation trying to use this radio in an emergency and you attract every zombie in a 10 mile radius!

author: Zero999
author_rank: Super Contributor
timestamp: February 07, 2018, 05:01:29 pm
content: I added more transistors, forming a bridge and simulated it. I've not bothered with the frequency divider part.I noticed that there was some cross-conduction, causing 6A current spikes being taken from the power supply rail. This was due to the storage time of the driver transistors and the solution was to limit the rise/fall time of the input signal, by low pass filtering it with R9 and C1. This fix will also need to be implemented on the previous circuit.The output saturates near to the rails. If LTSpice complains about missing models, or you can't get hold of the transistors, use TIP31 for BD131 and TIP32 for BD132, which will work but will have a higher saturation loss.