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I was curious about how driver excursion in a headphone corresponds to the volume that music is playing at.

For this question, let's use my current headphone as an example. It's the Audio Technica MSR7NC, a noise cancelling variant of the popular MSR7's.

Here are its measurements and specifications when the noise cancelling is off...

and here are its measurements and specifications when the noise cancelling is on.

So when I plug my headphones in to recharge them, I typically leave on the noise cancelling. According to the first chart I provided, the noise cancelling provides up to 15 decibels of noise cancellation in some frequencies, and a bit less in others.

Given this, for simplification, let's say that this results in the headphones "playing" some frequencies at 15 decibels for the 18+ hours that I'm not using them.

Then, let's say that I listen to the headphones for a few hours at normal listening levels, say 65-70 decibels.

I understand that decibels are logarithmic, so 65 decibels should be 10,000 times louder than 15 decibels, but I find it hard to believe that the drivers in the headphones are doing 10,000 times more work.

Does anyone have a way to estimate the excursion made by headphone drivers based on their diameter (45mm) and their volume of 15 decibels, at least relative to their excursion at 50 decibels louder? Finally, I want to be able to measure the total excursion of my headphone drivers after a given amount of time (like hours) at a given decibel. How many hours of active noise cancelling is equal to a few hours of normal volume listening in terms of driver excursion?

I want to know this because I don't want to switch my headphone's noise cancelling on and off all the time as the switch seems a little flimsy, but I also want to know what I'd be putting the drivers through this way (I charge them right next to my pc which is computing 24/7).

Thanks!

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  • \$\begingroup\$ The work done in noise cancellation is dependent on the noise in the environment. The speakers have to produce a cancelling noise of similar magnitude to the noise, attenuated by the passive ear muffs. The music or whatever will dominate unless it's turned down to low volume. If the noise you hear with the headphones off is comparable to your desired sound level, that's a really noisy environment. \$\endgroup\$ – Spehro Pefhany Nov 27 '17 at 7:20
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I understand that decibels are logarithmic, so 65 decibels should be 10,000 times louder than 15 decibels, but I find it hard to believe that the drivers in the headphones are doing 10,000 times more work.

Nature doesn't care about what you believe. But, there are reasons for what you think.

A sound wave of 65dB(something)* does have 10,000 times the acoustic power of 15dB(something), which is 100 times the pressure swing. However, it doesn't sound 10,000 times 'louder', because of the weird non-linear way our ears perceive loudness. The headphones don't use 10,000 more battery power to generate it, because they have a relatively high standing power consumption which dwarfs the actual electrical energy needed to create the sound wave, in other words, they are quite inefficient, especially at lower power levels.

  • dB are always relative to something, some reference. In the case of acoustic power, it's usually dB(A), see A-weighting on wikipedia for exactly what that means.
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  • \$\begingroup\$ I believe you are mixing up dB to be relative (i.e. a ratio w.r.t. to some kind of "unity", like 0.775V, 1Pa, 1mW or whatelse) and then sometimes also weighted, i.e. we consider a second "quality" of what we are measuring (frequency most of the times in electronics) and assign more or less "importance" upon that. \$\endgroup\$ – carloc Nov 27 '17 at 9:24
  • \$\begingroup\$ So a driver at 65dB would be working 10,000 times harder than the same driver at 15dB? That would mean that the driver excursion at 15dB would be absurdly small. \$\endgroup\$ – Anthropologist Nov 27 '17 at 19:14
  • \$\begingroup\$ @ChetSpalsky Yes, indeed. It is absurd how little movement the human ear can hear. \$\endgroup\$ – Neil_UK Nov 27 '17 at 20:12

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