# Human hearing

One of my dimwitted co-workers says that although scientist say we hear 20Hz to 20kHz, the average human can’t hear above 8kHz.

Please can someone show him wrong.

20 Hz to 20 KHz is an approximation. People vary, and even among individuals your hearing ability varies with age. Also, note that the human ear doesn’t have a “flat” frequency response. We tend to hear things around 3 KHz better than we hear things at say 12 KHz. Around 8 to 10 KHz our ability to hear does start dropping off, but most people can hear frequencies up to about 15 to 18 KHz. Very few people can hear frequencies above 20 KHz.

Same on the low range. Most people can’t hear 60 Hz. You often can hear “transformer hum” (the humming sound coming from electrical transformers) because you pick up on a resonnance at 120 Hz, rather than hearing the fundamental 60 Hz tone caused by the metal in the transformer vibrating.
20 Hz to 20 KHz is a good maximum range. 100 Hz to 15 KHz is probably more typical.

mmmmm, I think most people can probably hear a bit lower than 60Hz. The lowest note on a piano is around 27.5Hz, and good bass singers like J.D. Sumner and some of the Russian choir singers can sing notes in the range of 30-35Hz; it’s still quite audible. But I think the main part of the question was upper hearing ranges, which I’m not very familiar with. Here’s a list of frequencies looked at through musical eyes.

mmmiiikkkeee, perhaps you missed engineer_comp_geek’s point about overtones or harmonics. Sounds at a low frequency that are not perfect sinewaves (most aren’t) carry energy at 2x, 3x, and higher frequencies (always an integer multiple of the fundamental frequency). In fact, it’s actually pretty difficult to generate a sufficiently perfect sinewave to test hearing at low frequencies (though high fidelity equipment and especially good headphones are a nice start).

We did testing in our school in physics using a frequency generator and amp/speaker. Among other things, we tested high-freq hearing from 10-20 kHz, in steps of 500 Hz. What we found, of a class of about 50 19-28 year olds:

• The person with the worst high-freq hearing could only hear to 11 kHz.

• The mean high point for men was about 14 kHz.

• The mean high point for women was about 15 kHz.

• I had the best high-freq hearing in the class, able to hear up to 17.5 kHz.

Go to this site, and you can download a free tone generator.

Crank it up to 9 k and try it out. Most people will hear it.

PS I can hear the above tone generator up to about 13K. But my computer sound system only responds to up to about 15K, so I (or you) might be able to hear higher freqs on a better system.

That’s cool software, yojimboguy, but I question how well it is working on the high end. I seem to be able to hear all the way up to 18 kHz, and that seems unusually high. I can hear something all the way up to 20 kHz, but I don’t think it’s the actual tone per se.

I’m going to agree with Anthracite, I’m not sure what that program is doing, but it doesn’t seem to be doing too well at high frequencies. On my system (with a brand new Soundblaster Audigy Platinum, on Koss R-80 headphones) it’s making very audible noise right up to 20 kHz. I think it might be using a low sampling rate (22 kHz?) that’s screwing things up, but since there’s no documentation, I don’t know.

So I generated a .wav file (44.1 kHz, 16 bit) that steps from 8 kHz through 20 kHz in 1 kHz steps. Using that, I can hear up to 16 kHz before it goes silent to my ears. Then at 19 I hear something again, but it’s actually slightly lower of a tone than it was at 16, so I think it must be a harmonic- I think it’s the sound card’s fault, because I also hear it in a different set of cheaper plantronics headphones. I suspect that the audible range of both sets of headphones is way out of my hearing range.

But any way you slice it, 8 kHz isn’t really that hard to hear, even to my ears, which have been abused with years of that noisy racket that kids these days call music. I’d say that the OP’s coworker is indeed dim-witted.

Ditto about age dependence. There was one time at work when a piece of lab equipment was making a high-pitched noise. The two youngest technitians could hear it, but the 4 older people could not. A very clear age cutoff (about 30 in that case).

Very good point. The good old Hermann von Helmholtz did some interresting experiments on human hearing way back in the 19th century. I once attended a lecture where the speaker showed some of the experiments he had performed, and even used the same equipment as 150 years ago!
It turns out that the overtones are very important in deciding pitch! If you take a base frequency, and then add the harmonics (2x, 3x, 4x the base freq.) the perceived tone doesn’t change much. (It adds in ‘richness’ but it’s still the same pitch.) if you then remove the base frequency, leaving only the harmonics, you still perceive the same note! (It sounds a bit odd, but it’s definitely the same pitch.) By playing around with the harmonics you can make it sound pretty odd. It’s hard to explain, and has to be experienced.
Can yojimboguys software do this? Any other software out there that can?

Have you ever heard that whine your TV makes? That’s the television’s horizontal sweep frequency of 15.75KHz. Even though it’s not purposely fed to an audio speaker for our listening enjoyment, it is amplified quite a great deal by the Horizontal Output Amplifier and is usually present in large enough amplitude within a few feet of the set to be heard by those with ears that are good up to such high frequencies.

I’ve not noticed my TV set whining recently, maybe they’re getting better at shielding, or my hearing is going down the crapper (as I suspect happens normally as we age).

I ran the same kind of test that Anthricite talked about when I taught electronics classes on oscillators & amplifiers, and found that most students couldn’t hear above 16KHz. Interestingly, I turned off the generator & told the class that I was up to 17KHz+ and got a few students who claimed to still be able to hear the high pitched whine, so we may have a placebo effect happening to some extent.

On the top end, I would agree. Most people start petering out somewhere around 15k.

On the bottom end, a good instrument to test with is the pipe organ. The pipe organ is the only instrument that makes nearly pure tones. Nearly all pipe organs are capable of getting down very close to 20Hz. Most people can hear it. They are hearing the fundamental, not the mix of harmonics.

This debate has come up in my circle quite a few times (audiophiles). I also have worked as a radar tech (electronics) and own a tone generator and o’scope. When we have done these tests, all of us heard down to 20Hz or so quite well. I am quite convinced we were not hear harmonics.

The signal fed in was harmonic free and I am very comfortable the equipment was easily capable of reproducing it without significant distortion (adding harmonics).

http://www.velodyne.com/pages/productsp/hgs_series.html

Looks at the specs on the HGS-18. This was what was used during the test.

The idea that most people only hear 60Hz except by the harmonics can’t be right.

It is very true that people are much less sensative at each end of the range than at the center, but most people can hear pure tones in the 20-30 range.