I am hearing 7.5Hz audio here, how?

[Willen]

There is a attached file- there you can see a waveform of audio, picture captured from sound editing program. And also an audio file.

First I generated 7.6Hz audio from 'spectrum analyzer' software and recorded back to PC. I made zoom in the audio and got nice waveform of 7.5 cycles within a second. Waveform looks like on LTspice simulation.

According to rule we won't be able to hear less than 20Hz but why this 7.6Hz audio sounds like Harley Davidson bike, How? (I know something making me silly.)

 

[crutschow]

You must be hearing distortion harmonics from your amplifier and/or speaker. That might side like the low frequency exhaust pulses from a Harley idling.

 

[JimB]

The waveform you show is full of harmonics, it is a very distorted sinewave and distortion = harmonics.

Try generating a clean sine wave and listen again.

JimB

 

[alec_t]

To generate a clean sinewave you can use LTspice and export a .wav file; or you can use Audacity or similar audio software.

 

[MrAl]

Hi,

As others have pointed out if there are harmonics in the wave you might be hearing them instead of the base frequency. If it was a square wave, it would have harmonics that go way up into the kilohertz or higher even with an imperfect transducer.

Your wave looks like it has at least some even harmonics, and the first even harmonic would be at 15Hz, which is just a little below the "standard" 20Hz usually given for human hearing. 20Hz is just a guideline though not a set exact figure that applies to every human that was ever alive on the Earth. The first odd harmonic is at 22.5Hz, which is clearly above that standard, and the volume has something to do with it too as louder sounds will be easier to hear.

It's very hard to get a perfectly clean sine wave out of a transducer however, the transducer would introduce some distortion on it's own even with a perfect amplifier and perfect electrical sine wave. You would probably have to make a special transducer that was designed to have extremely low distortion.

 

[audioguru]

A cheap speaker will double or triple (or both) low frequencies because its cone is not a perfectly solid piston. A round speaker is better than an oval speaker.

 

[dr pepper]

At high sound pressures above which your ears can cope with you will 'hear' harmonics.

 

[audioguru]

At high sound pressures above which your ears can cope with you will 'hear' harmonics.

Isn't that called RAP music?

 

[Willen]

Hi all,
Thank you for your practicle description about distortion on signal, distortion on general speaker and about human hearing. I guess piezo produces less distortion than normal radio speaker.

To generate a clean sinewave you can use LTspice and export a .wav file; or you can use Audacity or similar audio software.

Oh wow, it sounds interesting, How can I make .wav file from LTspiceIV? I am using this simulation software but I never updated it. Can you guide me please!

 

[audioguru]

I guess piezo produces less distortion than normal radio speaker.

A piezo transducer produces a horrible frequency response with no low frequencies and many peaks and nulls at higher frequencies.

 

[tomizett]

As well as the low-order harmonics directly generated by your speaker, you also frequently get wind turbulence noise through the bass reflex port (if you have one) - this is heard as a "chuffing" sound.

 

[alec_t]

How can I make .wav file from LTspiceIV?

Go to Help/LTspice/Dot-commands/.WAVE

 

[dr pepper]

For the noise from the bass port you can minimise this by keeping the airspeed down, for a hifi a rule of thumb is 10% the speed of sound, there are standard caluclations for working this out, many pc cad packages do it for you.
You can also make sure there are no sharp edges which worsen the effect.

 

[crutschow]

Isn't that called RAP music?

I think the term "RAP music" is an oxymoron.

 

[ronsimpson]

Isn't that called RAP music?

The AudioGuru actually used the words "RAP" and "music" in the same sentence.

 

[audioguru]

I know that RAP is simply a person reading some text out loud with a beat in the background.
But the person has extreme African American slang and accent and cannot be understood.

On the radio recently there is a RAP song done by (black?) girls. Wrong, the girls are white.
Also there is a song by a (white?) guy. Wrong, he is black.
I was amazed when I saw them on an awards show on TV.