There have been a number of studies over the years trying to gauge the benefits, if any, of moderation and taking breaks away from loud noise or music. The short answer is that we are not really sure, but possibly. How is that for fence sitting?
Intuitively it does make sense that reducing the overall “time weighted” average exposure of loud music or loud noise would reduce any eventual permanent hearing loss, but this line of research is very difficult to pursue.
After all, it’s not just the peak or the average sound levels that we are concerned with but the durations of these levels as well. here is nothing wrong with being subjected to a few seconds of 100 dBA but there is something wrong with being subjected to 100 dBA over many hours- it’s not just the sound level, but the duration as well.
Now we get to the complicated part – how do we measure this effect, if indeed it does exist?
Traditional measures of temporary hearing loss (also known as Temporary Threshold Shift or TTS) measure a person’s hearing threshold before and after an exposure – the difference being a measure of TTS. This is typically performed with puretones and the result can be frequency dependent. But measures of puretone acuity have been shown to be simplistic. One can argue that by the time there is a measureable puretone loss in acuity, a lot of cochlear damage has already occurred. And this can be further complicated if this last sentence was to be rewritten as “One can argue that by the time there is a measureable puretone loss in acuity, a lot of cochlear and/or neural damage has already occurred.”
Puretone testing is easy to perform and gives pretty results we can see on an audiogram, but in the larger scheme of things, is a rather insensitive measure of neural or central auditory function. Puretone testing however can provide some measure of cochlear acuity, but for short exposures, tends to exhibit only a temporary shift.
Otoacoustic emissions (OAEs) have been shown to provide information on “function” and this takes into account some elements of acuity and also how the cochlea actually performs. While this has been a major step forward, and may provide different, but comparable information than puretones, OAEs still are rather blunt and gross measures.
These last couple of paragraphs demonstrate that this is not a straightforward question- Does taking a break from loud noise or music really work? We need to design and choose tools that can truly answer this question.
There are clinically expeditious tools that can be used that can be used but these tend to be more time consuming and are not found in all audiology clinics. “Evoked response” tools, such as ABR, seek to assess the neural damage or changes that occur as a result of loud noise or music. Actually tools such as ABR can assess a wide range of issues and pathologies and not just the effects of loud music or noise.
The work performed by researchers such as Jos Eggermont, Sharon Kujawa, Charles Liberman, and many others in the last 15 years, demonstrate that while the cochlea can return to normal function and acuity after loud noise and music exposures, there may be permanent neural structures “downwind” that do not return to normal.
That is, the puretone thresholds and the OAEs can return to a pre-exposure, or even normal state, there can be permanent neural damage that remains hidden. The popular media has quite astutely referred to this as “hidden hearing loss” and as clinical audiologists, we are just now starting to scratch the surface of this area of study.
It is quite possible that regardless of the results of well-controlled experiments that use puretone threshold acuity or OAEs, much damage remains that is “hidden” from the person and the audiologist.
In part 2 of this blog series, an article will be reviewed that deals with some of these issues and some suggestions will be provided that may allow us to pry into the realm of hidden hearing loss.