A few of you may have “dosage” on the mind in these times, for reasons we will not elaborate upon (Musical acoustics is all about making your life more fun!). Like many of the enjoyable things in life, a little bit of sound exposure can be quite enjoyable, but too much can be injurious to your health. Let’s work together to make sure your dose of noise* is within permissible levels.
*noise here refers to the refined & beautiful music you so love, not the incessant clatter and hum of urban and industrial life!
Continuing further on the theme of the last few weeks, we’re going to look at the methods used to calculate noise dosage and…drum roll, please…how to use TubeTraps to help lower your dosage while listening to music!
The General Idea of Dosage
Sonic events are usually quite dynamic, changing in level over time. This is utterly true in regard to musical playback. So then, how can one determine the dosage of noise exposure? A graphical example is shown below in which a time-weighted average is calculated over an 8 hour period for a fluctuating noise scenario. As you see, the peaks extend above the “equivalent sound level” (ESL) and the valleys fall far below. However, in terms of contributing to hearing damage, the ESL is the metric of concern.
For those of you who are mathematically inclined, the formula for calculating your percentage dose is shown below with variables explained.
↑ represents the anti-log
D = Percentage exposure (%)
TC = Criterion sound duration (usually 8 hours)
T = Measurement duration in hours
L = Weighted sound level
LC = Criterion sound level (usually 85 dB(A)
q = (Exchange rate parameter(dB)).
=10 for an exchange rate of 3dB
= 5/log10 (2) for an exchange rate of 5dB
Fore more details about calculating noise dosage levels, check out this link.
In a nutshell, the louder and longer you listen, the higher your dose and the greater your risk of permanent hearing loss.
How Room Conditions Play a Role
Ever notice how some rooms just seem a bit more “painful” to listen in? Well, this may be caused by a sustained noise level. Last week we repeated the phase “running reverberant noise floor,” which some of you may recall has a negative effect on the audibility of upper harmonics and transient detail.
To recap, the running reverberant noise floor exists primarily because of uncontrolled buildup of sound in the front end of room near the loudspeakers, where the energy is stored and (relatively) slowly dispersed throughout the room. The level and duration of this “head end ringing” obscures many upper partials and can make even quarter-notes indiscernable.
So what effect does this have on noise dosage? According to the chart and formula in the previous section, more time spent listening to a higher sound level increases the dose—and the potential for hearing damage.
How Can TubeTraps Help?
We’re glad you asked! The most direct way we have found to reduce the level of the running reverberant noise floor is through low end control in the vicinity of the loud speakers. Put another way, “TubeTrap” the front of the room!
By placing TubeTraps in the plane of the speakers (side-to-side and front-to-back) we knock down two of the worst offenders. And of course the corners behind the speakers build up and store massive amounts of bass energy.
Now, your system will quiet between notes, reducing the total noise dose delivered to your precious ears. And the whole setup sound a whole lot more musical to boot!