Do electro-mechanical sirens reach indicated rpms?

[Robert Gift]

Or does loading cause them to fall short a certain percentage of rated speed on the name plate?

Thank you,

[Daniel]

Use your ear. Using a Model 5 on 60 Hz. without a phase invertor for an example, if the motor is rated at 3,450 RPM and the siren has 12 ports, then the formula ((RPM)(ports))/60 will give a design frequency of 690 Hz. A nice "F" note. Take your laptop down to the siren site, set your NCH tone generator to 690 Hz., and when the siren activates, record the sound and compare it with the pitch standard. If you have a program that can recognize the recorded frequency, reverse the equation to find out the actual RPM. A lesser frequency may suggest that your theory is correct, or may be the result of mechanical interference, poor motor condition, insufficient voltage, or (highly unlikely in America) deviated line frequency.

[Robert Gift]

Good idea, Daniel.

What is NCH?
Why 690Hz? F ?

I have "imperfect pitch" --can get close but can be 50 cents off either way.
(I got an A tuning fork.
Later thought it was flat, then discovered it is A-435!!!!
Is this fork a hundred years old?!)

I rarely get to hear sirens.
Nor do I know what they are supposed to be sounding.

Did you see the Acura commercial where they are supposedly tuning an organ pipe -- with many pipes sounding. Funny, none of the pipes I ever tuned "rang" so well.

[SirenMadness]

NCH is a tone-generator software, which does cost money if you want to purchase it.

[Robert Gift]

Thanks Peter.

I have a tuning meter which produces several octaves of tones to which cents can also be added or subtracted.

A-440 seems now to be approaching A-444 because orchestra string players feel that their instruments sound brighter sharper.

In the 1800s A was 435.

When I heard Denver's [>=<] the notes blended so well together that I could not tell that it was a fourth.
SD-10.