# Can a pitch be perceived outside the range where it can be heard?

In an example on the wikipedia section on Binaural Beats it says that two sine waves heard as separate signals, one in each ear, which differ by 10 Hz will produce the perception of a 10 Hz difference tone.

Is that possible? I had always heard the lower threshold of pitch perception was around 20-30 Hz. So 10 is right out, right? Or is the mechanism of (ap)perception not bound by the same limits as the sensory apparatus?

• Would hearing a 10-Hz beating/oscillation of volume count as perceiving a 10-Hz pitch? – Dekkadeci Jun 15 '18 at 23:53
• That sounds (bad pun) like careless writing to make the arithmetic simple. FWIW the lowest fundamental frequency produced by (a few very large) pipe organs is 8Hz, but that tone is not meant to be used on its own and in some situations (and for some people) it is be perceived more as 8 countable "pulses" per second rather than as a continuous tone. Also it is not a pure sine wave, of course. On most "large" pipe organs the lowest fundamental frequency is 16 Hz. – user19146 Jun 16 '18 at 7:13
• Won't it be affected by the actual Hz, as in the difference between ,say, 40 and 50 is significantly different from 2000 and 2010Hz. – Tim Jun 16 '18 at 7:27
• The beat frequency is equal to the absolute value of the difference in frequency between the two notes. But don't confuse this with the 'resultant bass' phenomenon used to fake low notes in a pipe organ. – Laurence Payne Jun 16 '18 at 11:32

A 10Hz beat is not heard as a pitch, rather as a fluctuation of volume, but it is certainly detectable.

As a seperate topic, a low tone from, say, an organ pipe may not be directly 'heard', but our brains deduce its pitch from its harmonics, which ARE audible. We deduce 'A low-low C will have harmonics including the C above then G, then the next C, E...etc. I can hear THOSE notes, therefore there must be a low-low C'. And, perceptually, we actually HEAR the low note! This phenomenon is used in pipe organs to avoid the cost of immensely long pipes. http://www.pykett.org.uk/resultantbass.htm

If I tap my hand on my desk at 5Hz, I hear the taps, but they're perceived as individual events, not a sustained note. The perception of pitch emerges when events happen fast enough.

Here's a video about it, with a demonstration at the timestamp in the link :

So the answer to your question is basically "no". Pitches below the normal hearing range are heard, but not as pitches.