Talk:Hearing range

Article revision

I can contribute the following text, which is modified and expanded from my page on testing the hearing of whales and dolphins. I'd like to get a little feedback before simply replacing the current text. I think the current text is problematic in several ways.

An audiogram is a graphical representation of how sensitive a subject is to acoustic stimuli across a range of frequencies. Frequency is placed on the X axis, usually with a logarithmic scale, and threshold values, usually in decibels, are plotted on the Y axis. For a behavioral audiogram, researchers obtain the needed threshold values by training subjects to respond to test tones with a specific behavior, which allows the tester to determine which tones have been heard and which were not heard (but see detection theory). For most humans, this may be accomplished by asking them to press a button or speak a word when they hear a test tone. From repeated trials, researchers estimate the threshold of hearing at each test frequency. Researchers do the same for a number of frequencies of test tones to find the audiogram of the subject.

For a behavioral audiogram, the subject is trained to make a response to an acoustic stimulus. The acoustic stimuli are given at many different frequencies and amplitudes, and an estimate is made of the threshold of hearing for each frequency. This approach contrasts with audiograms taken using electronics to pick up the faint signals of the brain's response to those stimuli, or neurophysiological audiograms. A common approach to obtain a neurophysiological audiogram is to monitor the auditory brainstem response (ABR).[1] While a neurophysiological audiogram by ABR has the advantage of not being dependent on having trained subjects, it has the disadvantage of requiring even more sophisticated equipment and impeccable technique in order to carry it off. Also, neurophysiological and behavioral audiograms do not usually agree precisely, even when taken on the same subject. A neurophysiological audiogram tends to indicate several decibels better sensitivity across the tested frequencies than does a behavioral audiogram.

A neurophysiological method for human subjects that is not as precise as ABR, but which can be accomplished with less complex equipment, relies upon otoacoustic emission. The healthy human ear not only transduces received sound energy, but also produces evoked otoacoustic emission of sound in response to acoustic stimuli. A small microphone placed in the external ear canal can pick up these small signals and indicate that the ear can react to a particular stimulus, or indicate a hearing deficit if no response occurs to a normally audible test tone. Such a technique is useful for constructing an audiogram of a human subject who cannot complete a behavioral audiogram, as in severe cases of autism.

As anthropogenic noise becomes more widespread, concerns about impacts of noise on animal populations grows. Audiograms for species become important tools for researchers and policy makers to take into account when dealing with anthropogenic noise. Unfortunately, relatively few species of birds or marine mammals have had audiograms constructed for them. For example, there is no audiogram of any type available for any mysticete cetacean.[2]

A problem with audiograms of non-human subjects is that there is often a tendency to use an audiogram obtained from a single subject and treat that as a representative audiogram for an entire species. This famously led to many years of confusion, from 1972 to 1999, as researchers believed that killer whales could not hear frequencies above about 32 kilohertz, based upon an audiogram of one subject. Later, audiograms taken on other killer whales revealed that their hearing was similar to that of other odontocete cetaceans, with ultrasound sensitivity up to about 120 kilohertz, indicating that the original subject had extensive high-frequency hearing loss.Szymanski et al. 1999

Another issue concerns the completeness of testing for an audiogram. For decades, shad were considered to have an ordinary audiogram for fish, with peak sensitivity under 1 kHz and an upper limit of hearing between 1 and 2 kHz. Further testing, however, demonstrated that shad actually could detect ultrasonic sound up to about 180 kHz.[3]

Wesley R. Elsberry 08:07, 12 April 2006 (UTC)

The above was copied from Audiogram when the animal content of that page was moved here. I think this is very useful, but not strictly audiometry as it relates to absolute not relative measurement. --15:52, 5 March 2008 (UTC)

Contradicting Information

I know wikipedia is not the best source for "reliable" information (or at least, that is what is drilled into our minds every time we consider using it as a resource), but I am trying to discover information relating to the maximum hearing range of dogs (and to a lesser extent, humans). Unfortunatly, the image provided (the dark coloured bar graph(?) with numerous animals's hearing ranges) contradicts the text information, citing a maximum hearing range of 23kHz for humans (20kHz in the text, and most other resources) and 45kHz for Dogs (60kHz in the text, and little information given in other resources). Clarification on this information or links to more recent or non-conflicting sources would be appreciated. Thanks, Jonzay (AKA --203.214.151.1 (talk) 12:50, 20 May 2008 (UTC))

After a year it appears this hasn't been resolved. Human range in the article is 16-16384hz (the high number looks suspect even by itself; 5 signifigant figures but the low measurement is only 2 signifigant figures? and it so happens to be EXACTLY a power of 2?), but the graph gives a much different 64-23000hz. Anyone know what's up? 69.255.248.13 (talk) 00:09, 21 June 2009 (UTC)

Both the text and the bar graph are incorrect. The text contradicts the bar graphs at several places and for several species. In fact, human hearing is beyond the range in the text. 16 Hz is generally accepted as the low frequency detectable by the human ear. 16 KHz is much too low for the upper range. 20 KHz is given because it is generally the high frequency limit of speakers, but humans have shown teh ability to hear frequencies as high as 21 KHz, though this is rare. Whether higher frequencies are detectable and whether resultant frequencies or increased amplitude due to these resultant frequencies, are detectable is still debated. Marchesa (talk) 06:12, 14 July 2009 (UTC)

The range of human hearing varies between individuals depending on many factors including age, sex, and ethnic background (various genetic variations passed on which cause variations in hearing structure size, shape, sensory distribution, neuronal sensitivity, etc.; all of which have an impact on the hearing range of the individual). Some individuals can hear very low or high ranges which others never had any sensitivity to. Many of the numbers in the article seem to be generalizations (which is appropriate) however, there should be indication that: a) these are general/average ranges; b) what the known extremes tend and/or are known to be. With the advent of digital music, individuals with out-of-the-general range hearing have been easier to find as those with higher ranges are more prone to indicate they hear digital artifacts in the reproduced audio (such as music that has been 128b mpeg3 encoded which is good sound for general human hearing, but leaves many "chirping" sounds in it which higher range listeners can hear, but are mostly unheard by these individuals with 192b mpeg3 encoding). Someone with good citations should make adjustments to this article.

Insects, etc. animals, and even plants

Make sure to mention each major type of animal, e.g., crickets obviously are chirping for their compatriots to hear.

Even mention plants: do some species do bad near (what frequencies of) noise? Jidanni (talk) 20:03, 18 June 2008 (UTC)