How to do this by a speaker

[dr.power]

Hi guys,

I have 2 function generators. one is producing a 1kHz sine wave and the other is producing a 2KHz of sine wave. Now I want to simulately give these 2 signal to A speaker, How can I do so?
What frequncies I will get at the output of the speaker (in air I mean).

Thanks in advance.

 

[audioguru]

Make an active analog mixer circuit or use two resistors connected together at the input of the power amplifier. Each resistor is fed from its own function generator.
The speaker will produce 1kHz and 2kHz at the same time just like if there were two people singing at the same time.

 

[dr.power]

Thanks Guru,

By mixer are you meaning a modulator or you mean a Summing circuit?

 

[audioguru]

An analog mixer is a summing circuit.
A modulation circuit has a carrier frequency and a modulating frequency that changes the amplitude (AM) or the frequency (FM) of the carrier.

 

[gary350]

It will sound like a police siren if you put 2 different frequencies to a speaker. I built the same thing using two 555 times many years ago.

 

[audioguru]

The dial on a modern telephone is Touch-Tone and plays two frequencies at the same time.
In music, two or three frequencies played at the same time is called a Chord.
They don't sound like a Police Siren.

In Europe, a police siren is two frequencies alternating one after the other: the first frequency is played by itself then turned off, then the second frequency is played by itself then turned off, over and over.

In North America a Police Siren is a single continuous tone that slowly changes its pitch (its frequency) up and down.
There is a hound dog near my house that sounds the same when he hears a police siren.

 

[cr0sh]

The dial on a modern telephone is Touch-Tone and plays two frequencies at the same time.
In music, two or three frequencies played at the same time is called a Chord.
They don't sound like a Police Siren.

In Europe, a police siren is two frequencies alternating one after the other: the first frequency is played by itself then turned off, then the second frequency is played by itself then turned off, over and over.
In North America a Police Siren is a single frequency that slowly changes its pitch (its frequency) up and down.

I'm not sure how true this is any longer; I was recently (about a week ago) listening to a BBC radio broadcast on NPR, and noted how they were reporting in Britain (on something or another), and there was an emergency vehicle siren in the background - that sounded like an "American" siren! I've noticed this on occasion in the past, as well; I'm not saying they all sound like this, but maybe a transition is occurring, or something else (then again, I have heard the opposite as well - I'm not sure what is going on)...

 

[Nigel Goodwin]

I'm not sure how true this is any longer; I was recently (about a week ago) listening to a BBC radio broadcast on NPR, and noted how they were reporting in Britain (on something or another), and there was an emergency vehicle siren in the background - that sounded like an "American" siren! I've noticed this on occasion in the past, as well; I'm not saying they all sound like this, but maybe a transition is occurring, or something else (then again, I have heard the opposite as well - I'm not sure what is going on)...

I suspect AG is stuck well back in the last century

Two tone sirens vanished decades ago.

 

[audioguru]

I visited the UK in 1964.

 

[Nigel Goodwin]

I visited the UK in 1964.

That explains a lot!

What were police sirens like in Canada in 1964? - certainly not the current ones!.

 

[audioguru]

Police sirens in 1964 sounded almost the same as now. They were an electric motor wind blower thing and varying the speed of its RPM made the frequency go up and down. Here is a video of a 1964 police car: https://www.youtube.com/watch?v=9JKEPD8Gf98&feature=related

Videos of old British police cars sound like BEEE-BOOO-BEEE-BOOO.

EDIT: Here is a 1956 Ford police car TV commercial with the same siren sound as today:
https://www.youtube.com/watch?v=CVcgUBOX9cc

 

[cr0sh]

I suspect AG is stuck well back in the last century

Two tone sirens vanished decades ago.

That's too bad - I kinda liked 'em... Any idea on why they switched?

 

[audioguru]

Modern electronic sirens make lots of different sounds just like car alarms that are triggered by any sound nearby or by themselves.
Most people ignor car alarms because they are triggered too often. Since modern sirens sound the same then people also ignor them.

 

[WTP Pepper]

An analog mixer is a summing circuit.
A modulation circuit has a carrier frequency and a modulating frequency that changes the amplitude (AM) or the frequency (FM) of the carrier.

Depends. In an audio mixing desk then mixing is the addition of channels, however RF signals are analogue levels in a conventional receiver. A mixer in such a circuit is actually a multiplier. Used to produce an offset IF frequency from a result of multiplying an incoming RF signal with a locally generated oscillator.

A sum of two sine waves is twice the Sine, of half the sum times Cos of half the difference was the little poem we were taught.