Ear Ache: Listener fatigue and other mythology.Part 1.

It was about 20 years or so ago and I was sitting in front of a brand new hifi system my Girlfriends’ flat mate had just bought. He was a young man, in his mid twenties, working in the City of London and was earning beyond what normal graduates would be earning at that age. I, on the other hand was working for toffee, writing editorial and reviews at Hi-Fi World magazine. The hifi system in question had as its centre piece an amplifier from a well know brand of the time that by chance I had just written a review of. My tactless younger self sat down with the chap and said to him that he should have spoken to me first and that his ears would be hurting after less than a hour of listening even at low levels of volume. A few days later the flat mate got in touch to tell me I was right. Some attribute this phenomenon to what they call Listener Fatigue though I am not so sure.

Listener Fatigue[1. http://en.wikipedia.org/wiki/Listener_fatigue], not as far as I am aware a medically recognised term, is attributed to tiredness, discomfort and some pain after prolonged listening to music and usually at louder levels. In the case in question, however, we have less than an hour’s listening and at not necessarily high levels of loudness yet the pain and discomfort is genuine. I have had and have anecdotally heard similar complaints from others while listening through headphones. An often, but not always, telling sign of a problem is when vocals spoken or sung in a recording are sibilant or seemingly ‘shouty’ in reproduction. Also if certain instruments like high hat cymbals are sounding obviously ‘splashy’ rather than clean. As you can see from my use of ‘Latin’ terminology I have yet to find a source of medical or other academic verification of the cause. To this end I thought it worthwhile posting on a number of audio fora (or forums) which we sponsor to see if I’d get a few more view points and who knows some pointers to academic studies. To put it mildly, in just a couple of days the response was vast and to say the least, quite varied. I placed the threads in Audiokarma, Pink Fish and Audio Circle. Although one or two tangents are taken there are clearly quite a few declarations of faith in the phenomenon. Though the number of theories as to the cause outnumbers the respondents by some margin. Putting to one side my own scientific leanings for a moment, a little bit of pseudo-science and straw polling statistics suggest strongly that at the heart of it all is a mixture of poorly balanced presentation of the audio and, of course, non linearities in the reproduction. In other words, distortion [2. http://en.wikipedia.org/wiki/Distortion] [3.  http://gedlee.com/downloads/Distortion_AES_I.pdf][4. http://www.gedlee.com/downloads/Distortion_AES_II.pdf]

Within a few hours of me posting the threads one of our very well respected dealers sent us a message saying, “No disrespect – but what do you guys know about listener fatigue? Sonneteer kit is *most* notable – above all else – for completely lacking it: lovely velvety tonality!”. Yes thank you and a product would not leave our test benches if it were to behave otherwise. Saying that, I was recommended an interconnect cable recently to try, but it turned our “velvety” test reference system into an unbearable listen (again at normal listening levels) after about 10 minutes. With the cable connected, initially the system sounded more present, more detailed and perhaps extra real. Well as I wrote not too long ago, the human ear is exceptionally sensitive and so responds to tiniest change in pressure in the airwaves. To give you an idea in numbers, the human ear threshold of hearing is less than one billionth of atmospheric pressure [5. Hyperphysics, Georgia State University]. So there were clearly some changes in the sound, if slight, disturbing enough to cut short my pleasure.

Ok so I did come across a number of academic papers alluding to the subject (found in some of my footnote references scattered about this article) but not quite addressing directly. One of the more interesting reads was on  a loudspeaker manufacturer whose customers are often associated with Sonneteer product, Harbeth’ website [6. http://www.harbeth.co.uk/usergroup/showthread.php?1813-Listening-fatigue-how-does-Harbeth-avoid-it]. Though more focussed on loudspeakers it certainly presents an interesting educated view of the subject. Much, again, leans towards audible distortion and non-linearities in particular audio frequency bands and so on. Upper mid band audible frequencies between 3KHz and 5KHz, for example, seem to be mentioned a lot as too are accentuated lower mid to upper bass sounds. My instincts lean me to agree with much of it. Also a lot has come up in the fora which is credible but there is very little scientific flavour to any of it.

For now, I can conclude that the accuracy of the presentation of the recorded material is key. By that I don’t necessarily mean absolute verbatim reproduction, but a true re-presentation of the essence of the recording. This applies equally when designing an in car system, a portable music system, a TV sound bar or a high end, high fidelity system. Good, quality design will deliver at all these levels. We buy these products to be entertained by their delivery. If we don’t like it we will simply switch off, consciously or otherwise. In the meantime, I will continue to follow the fora as the conversations unfold, explode and tangent. There may even be an Ear Ache Part 2 as I learn more.

Haider Bahrani is Managing Director and one of the founders at Sonneteer.

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