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I am playing with a speaker and a microcontroller and in some documentation the speaker is called buzzer. The assistant told us that is a mistake and we are dealing with a speaker.

I am wondering what exactly is the difference between the two, where can I learn more about these kind of devices and if there are any other similar or not so similar devices that are able to output sound.

EDIT: What is the difference between a piezo buzzer and why isn't buzzer a tag but piezo-buzzer is a tag ?

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    \$\begingroup\$ Tags are created by users with enough points, and the if the tag becomes useful it doesnt get cleaned up or removed. So far that has apparently not happened, but if you build up enough points you can create the tag and see what happens. if all buzzers are really piezo buzzers then there you go it is covered. \$\endgroup\$ – old_timer Feb 26 '17 at 16:34
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    \$\begingroup\$ A relay makes noise when it clicks, if that counts (e.g. turn signal clicks). And motors/gearboxes make noise when they move. And also... \$\endgroup\$ – Jason C Feb 26 '17 at 23:32
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    \$\begingroup\$ In normal English usage, a buzzer is a device that makes one fixed sound when it is activated, but a (loud)speaker reproduces the audio signal that it receives. Of course a very small speaker won't give a good reproduction of speech or music, but at least it attempts to do that. But note that some high-quality loudspeakers use piezo-electric devices to produce the sound - so "piezo" doesn't necessarily imply "buzzer." \$\endgroup\$ – alephzero Feb 27 '17 at 4:01
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    \$\begingroup\$ Inductors certainly make a sound: see complaints about "coil whine" on some power supplies. \$\endgroup\$ – pjc50 Feb 27 '17 at 16:29
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    \$\begingroup\$ @Ideogram A typical board-mounted cap won't make much sound, but "a little sound" is possible. Most cap types can be microphonic too. As for non-ordinary caps, consider electrostatic speakers. \$\endgroup\$ – Jamie Hanrahan Feb 27 '17 at 16:49

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A buzzer usually has an oscillating transistor circuit inside - to make the buzzing noise when voltage is applied, so it makes a tone.

Applying voltage to a speaker will not make a tone, so you'd need an external oscillating circuit (e.g. a 555, or transistor oscillator). A speaker can play all kinds of sounds, however due to its built in circuits, a buzzer may not be capable of playing tones other than its oscillator's tone.

Buzzers are usually piezo buzzers - based on a tiny bit of crystal inside. You can usually see a metallic flat surface there, with a larger box/circuit underneath for the built in oscillator circuit.

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    \$\begingroup\$ Piezo buzzers are essentially piezo speakers with an oscillator circuit attached \$\endgroup\$ – Chris H Feb 27 '17 at 9:53
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When someone is "buzzed" into the house, its with a relay (electro-mechanical) sound-maker.

A relay, wired as normally closed, but able to break the circuit, is a buzzer.

schematic

simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ No need to downvote this. It's the original oscillator from the 19th century. It's still useful. Without it we probably knew nothing about radiowaves, radios and X-rays. Even the ordinary ringing bell is an enhanced version of this - added another coil to pull the switch (and the hammer) actively back. \$\endgroup\$ – user287001 Feb 26 '17 at 15:01
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    \$\begingroup\$ @user287001 that doesn't make it an answer to the question at hand, however. \$\endgroup\$ – hobbs Feb 27 '17 at 5:48
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    \$\begingroup\$ This is the origin of the term buzzer, and it's quite obvious that it can only output one sound unlike a speaker (it changes a little with voltage but not much). \$\endgroup\$ – Chris H Feb 27 '17 at 9:49
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    \$\begingroup\$ @user287001 I've seen electric bells that just use a big spring for the return. \$\endgroup\$ – Chris H Feb 27 '17 at 9:49
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    \$\begingroup\$ @ChrisH One dome ringing bell can well have a return spring. The two dome bell can make more noise and both hitting directions can sound equal with the push-pull coils. \$\endgroup\$ – user287001 Feb 27 '17 at 10:16
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Traditionally a buzzer was a device designed to make noise. Traditionally it would have been an electromechanical device. It would typically be supplied with DC and the oscillations would have been produced by an electromechanical process inside the buzzer.

A speaker was/is a device used to reproduce sound from an electric waveform with the sound coming out being at least a passable analogue of the signal going in.

However in more recent years the world has moved on. The relative cost of electronics in general and micro controllers in particular has dropped compared to the cost of electromechanics.

So nowadays instead of a traditional mechanical buzzer we often use "piezo sounders". These are something of a half-way house between the traditional buzzers and speakers. They are driven with an audio-frequency waveform, typically a square wave. That allows multiple tones for different types of alert and even allows playing crude music. However they are not designed to reproduce arbitrary audio with anything like reasonable accuracy.

Whether to class piezo sounders as "buzzers", "speakers" or neither is somewhat a matter of semantics.

I suspect the "mistake" is actually a case of your instructor disagreeing with whoever wrote the course material rather than a real mistake but without more detail it is hard to be sure.

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  • \$\begingroup\$ To elaborate on "piezo sounders"... These have a piezo speaker inside them, but the piezo element is inside a highly-tuned Helmholtz resonator. Although they can produce different frequencies (by driving them with different waveforms), the resonator means that this one frequency produces very much louder sound than anything else. \$\endgroup\$ – Graham Feb 27 '17 at 13:07
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The buzzer gets the operating voltage, mostly DC and outputs sound. It can be a combination of a speaker and an oscillator. The piezo sounders are thatlike buzzers. The speaker in the buzzer can be optimized for a single sound, no need to reproduce music.

In the good old days the buzzer was an electromechanical releay oscillator that was noisy enough without any speaker. The relay itself vibrated. For stronger voice the moving part of the relay can have quite large area. Surely those apparates are still available due their robustness. The relay was connected to break its supply voltage as soon as the relay had pulled. For example the horn in a car can well be thislike electromechanical buzzer.

The speaker needs AC audio signal that makes its membrane to move and produce the sound. The speaker must operate in wide frequency area to have any value.

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Another purely electric noisemaker is a plasma arc in the air - the same is used for welding and in ultra high luminosity arc lamps. If the current is modulated with audio signal, it surely can be heard. The low mass of the plasma suggests a high maximum frequency. I have not seen any real devices in front of me, but searching "plasma tweeter" gives several hits.

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Another type of noise maker is the Siren which uses a different technique...

Most modern sirens use two concentric cylinders, which have slots parallel to their length. The inner cylinder is rotated by a motor while the outer one remains stationary. As air under pressure flows out of the slots of the inner cylinder and then escapes through the slots of the outer cylinder, the flow is periodically interrupted, creating a VERY LOUD tone.

enter image description here

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    \$\begingroup\$ The diagram is of a klaxon rather than a siren. (Motor drives the ratchet which engages the stud, which vibrates the diaphragm) \$\endgroup\$ – peterG Feb 28 '17 at 13:36
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Buzzer is speaker which produce certain sound like "buzz" but it can't be use to play your favourite song because has inbuilt oscillator which produce same waveform repeatedly.... Speaker are transducer which produce sound for analogous waveform input into it.

SPEAKERS -------RUNS ON AC (Square wave, triangular wave ,etc.)

BUZZER -----------RUNS ON DC

No other things than speaker and buzzer are available which produces sound.

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Another electromechanical noisemaking device is the chime door bell. Unlike the relay approach it uses a solenoid to much a clapper which then hits a chime bar. When the voltage is removed the solenoid returns by a springto hit a deifferent chime bar of a different pitch, producing the classic "ding-dong" noise.

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Buzzers:
a) are triggered by a DC signal while speakers are driven by an AC sound signal.
b) produce a buzzing sound while speakers produce any sound

Buzzers are one of two types:
a) piezo buzzers that use the piezoelectric phenomenon to vibrate their membrane (the most common type and most efficient in audible dB per Watt)
b) magnetic buzzers that contain a tiny speaker but their wee membrane can only reproduce high pitch sounds (the least common type but with the smallest footprint)

More sound related electronic devices are beepers, sirens, ultrasonic transducers (have a look)

I don't know about the tag but probably because piezo buzzers are more common

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Exists probability that you will got somewhere buzzer device with internal frequency generating circuit.

But most probably, you will got device, which just transforms electricity to sound waves.

For such devices, the most important features - are their resistance and loudness (when have comparable size/weight), and unfortunately, exists extreme difference of piezo vs electromagnetic speakers in these.

For resistance: most small electromagnetic speakers used in computers have resistance approximately 8 Ohm.

piezo buzzers are very differently, physically equivalents to serial connected capacitor and inductance, but for case of microcontroller (Arduino) could considered to equivalent of 100 Ohm resistor.

For loudness - electromagnetic speaker is magnitude loader than piezo.

Conclusion - in most cases, piezo could been directly connected to digital cmos outputs (for better safety, you could wire it with 150 Ohm current limiting resistor).

Electromagnetic speaker needs some source of high current, and sure, for higher quality sound this source should have linear characteristics, and most microcontrollers could not feed high current.

But in case of microcontroller, could been used some simple circuit, like transistor switch circuit (open collector transistor switch circuit).

And sure, in case of electromagnetic speaker, you should use some sort of DC current limiter, for example, attach capacitor between mc pin and transistor, or write program which will not feed speaker with constant current.

Update: for other interesting things, I remembered, that any transformer (or just any coil with ferromagnetic core), could output sound.

It's very common, when power transformers output high sound. For example most TV's output it. Usually this is not very loud, but in silent room could hear.

Also few times I have hear high sound from voltage stabilizer, when computer run some programs, because power supply of this computer does not have PFC :)

Few times I have hear ring of analog voltmeter, when used some high power device like welding machine.

Update: About coils with cores - remembered, noise is one of things, with which people making/using brushless electric motors struggle.

Because brushless motors are some combination of coils with cores, they output unwanted sounds. And in most cases, people used high frequency currents, so these motors output ultrasound, which people don't hear. In some cases, controller electronics could not make control currents with high enough frequency, and could been hear sounds like squeaks or even screams.

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