Ety power handling and other questions - Page 2

Wodgy, I tried the -80 db at 1000 hertz. I have to crank the volume all the way up before I can hear it and the music is way too loud. Are you sure you don't mean -10 db assuming the dynamic range is 90db to get that maximum celiing of 80 db?

I also tried -70 db and -60 db. Each successive test lowers the volume knob.

Re: Off Topic

No way! That's so cool! LOL, I gotta see that. I got my avatar off the web -- I was doing a search one day and randomly ran across it on a site somewhere.

Oh wait, i figured out what was wrong with my reasoning. If I make a -80 db test tone and crank it up till I can barely hear it, then I have a dynamic range of 80 db above the threshold.

How do we know the amplifier doesn't scale the signal a funny way such that the 80 db of dynamic range is actually equivalent to real 80 db of sound energy?

Pedxing, glad you figured it out. I was going to post a couple of sound files with tones at -80db, just in case that was the problem, but alas my evaluation version of Cool Edit Pro recently expired. I'll try to post some sound files later in the week.

Ideally, a doubling in voltage on the wire should double output levels (voltage for the amp, sound pressure for the cans). This may not be true in both the amp and the cans. However, I'd venture that the approximation is pretty good in an average amp. If you really wanted to, you could remove the amp from the equation by trying a signal generator (the kind they use with oscilloscopes).

It's reasonable to suspect that headphones with large drivers (particularly the Senns) will not be entirely linear. But since the Etys have such small drivers, it's probably reasonable to assume that they are fairly linear (because the drivers have low inertia). However, even if they're not completely linear with voltage, the margin of safety is in your favor, because some of the voltage potential will be wasted overcoming inertia. So a doubling of voltage potentials will work out to *less than* a doubling of sound pressure levels.

I don't see why people are so worried about damaging their ears with ety's. it doesn't matter WHAT you're wearing, high SPL levels will hurt your ears no matter what! So what if ety's are closer to your eardrums? they won't kill your ears any faster than a pair of sennheisers at an equal volume level.

kelly,

There is no obstacle to taking out one Ety in order to compare the loudness of the outside world with what the Ety is feeding the other isolated ear. But that's not likely to be fully reliable with Ety's or any other headphone because perceptions of levels of sensations tend to be relative rather than absolute. If you've been hearing something quite loud, normal levels will seem rather faint, just as, after taking your hand out of hot water, even fairly warm water will seem cool.

On the other hand, if you've been listening to something quite soft, exposure to normal levels will seem unusually loud. Therefore, Wodgy's observation that things sound abnormally loud to him after an Ety session, should be particularly reassuring. (But I can't say that I've noticed anything of that sort in my own case.)

However, sensations of pain and discomfort, while not invariable, are much closer to having an absolute threshold. That is, they are often--but certainly not always--independent of recent experiences.

When at a concert some particular sound has you saying, "Wow! Way too loud!" I suspect that you are responding not to how much louder it is but to the discomfort that it produces. Everything (from decent seats) at most pop concerts will be extremely loud by everyday standards--so loud that you can't hear normal conversation and barely understand shouts. Chances are that you would be safer to have the earplugs in whenever ordinary speech can't be heard plainly.

Although the pain and discomfort standard isn't absolutely reliable (because of desensitization with long-term exposures), it's about the best indicator we have. SPL meters held near headphones will not necessarily accurately reflect the levels when the can is clasped tightly to your ear and bouncing the sounds back at it. Where, in fact, has anyone seen scientific measurement of SPL's for headphones while in use?

Finally, Neruda has a good point. There is no special reason to doubt your ability to evaluate loudness just because the source is close to your eardrum and well isolated. The net SPL at your eardrum is what must be watched irrespective of how it was delivered.

Since the Ety's are sealed, can the pressure (though low pressure) be properly released from ear canal as normal headphones? Will this cause any damage to ears?

Pressure, when present in a normal ear, can be released (or, let's say, compensated for) from behind the eardrum through the Eustachian tubes into the pharynx. But there may be a confusion here:

We could be talking about the pressure during insertion as a seal is obtained and air is trapped behind that seal and then compressed as the earphone is seated in its final position. You could let the Eustachian tube take care of this, or momentarily break the seal by distending the ear or twisting the stem of the Ety. But this sort of pressure is transitory, at most a one-time event upon each insertion. In my own case, I barely notice it, and it seems to take care of itself.

But, we could also be talking about the sound pressure level (SPL), the pressure created in the ear by sound as successive waves of air compressed and thinned-out strike it. These pressures continue for the duration of the sound. However, they are no less for Ety's than for any other sound source. Neglecting for the moment the subjective side of perception of volume, the Ety's push just as hard against the eardrum for a given loudness as speakers or instruments do.

Because of the Eustachian tube, there is in the ear no perfectly sealed system, but, even if there were, there is no special worry about the pressure from sound--except, of course, to see that it remains at levels below what would damage the ear. The pressure comes and goes; it's not like applying pressure from a pump, higher and higher levels with each stroke. Even with a perfect seal, the driver compresses the air in front of it while the eardrum responds by withdrawing. Think of the driver and the eardrum as coupled by the air so that they make movements that correspond to each other. What's important for preventing damage is for the excursions not to be too great. This dance should not get too violent.

Those excursions can be too great regardless of how much or little the ear is sealed. High pressures from excessively loud music can burst eardrums even in open ears. Long before those levels are reached, less obviously destructive sounds can ruin the cells in the cochlea that respond to them.

paranoid - Exhibiting or characterized by extreme and irrational fear or distrust

That is to say... I make no defense that my paranoid feeling are rational. It may be completely irrational to have this fear but it often takens more than someone else's rational state of mind to alleviate someone being being paranoid.

I agree with Neruda's assessment that it doesn't matter how the sound reaches the eardrum--it's in the amount that reaches it and over what length of time. Thus, if the same volume level is reaching the eardrum from the Etymotic as another headphone, they are equally dangerous. I agree. I never meant to dispute this.

What I question is--How does one determine objectively what this amount is. Raising the point that I can't accurately determine how loud other headphones are doesn't make me less suspicious of the Etymotic, it just makes me more suspicious of everything else.

Well, kelly, paranoia is a little strong. Can't we settle for, maybe, phobic?

Regardless, what I'm suggesting is that we have as much reason to fear any sound as to fear the sound from Ety's, and you have taken that point, although I didn't mean to make you more consistently paranoid--ah, phobic--but rather more consistently confident.

Since the ideal objective measurements don't exist for what we hear, I suggest that we use what nature has given us, the indications of pain and discomfort, which seem to keep most of us hearing quite well for most of our lifespans. The exceptions are those who tolerate and sometimes deliberately try to "overcome" the pain and discomfort, especially over long stretches of time. You very paranoid--er, phobic--nature would make you an unlikely victim of preventable hearing loss.

Have a little faith in the natural protective systems. Discomfort in your hearing is rather good compared to some others. You have to learn by experience when you're skin is going to turn red before you will move out of the sun or put on some blocker. Even without UV measurements wherever we happen to go, we mostly do learn and don't get skin cancer. At least with hearing there's not so much lag time between the discomfort and its causes, and the response needed--to turn it down, plug it out, or leave is usually much more available. than shade and lotion.

Kellly's question is tough to answer. It is possible to damage your hearing with the ER-4 as well as any headphone or speakers. It is a matter of Sound pressure level and time. The fact that the ER-4 sits closer to your eardrum is irrelevant.

The links to safe listening levels is available on our web site and I gave links to Kelly. We do sell a 2cc coupler for $15 that fits on the radio shack sound level meter. This will allow you to test insert earphones such as the ER-4, and correlate it to eardrum pressure. This works easiest with pure tones. You can get a pretty good idea using A-weighting and slow measurements with the sound level meter. You could also monitor voltage output to the headphones and use otput limiting to limit the level. Sony attempted something like this with their AVC/avl? Unfortunately this device is calibrated to the paticular headphones supplied with the players. This didn't work to well when I tried it. As an earlier post stated if the ER-4p puts out 100dB SPL with .2V input it will put out 106dB SPL with .4V input. The linearity is very good up until the unit starts distorting. Although the ER-4 will put out 122dB SPL maxiumum, the distortion level would be too much to bear before you got there.

The minimum audible pressure (MAP) is close to zero dB SPL near 1kHz. At low and high frequencies is slopes up to about 40dB SPL. Don't quote me since I don't have the article at home.

I will post more when I get more time, but I have been very busy lately.

Don Wilson
Etymotic Research

The link Don referred to was this one:
http://www.etymotic.com/hifi/fyi.html

I cannot find this product at Etymotic's web site. All I find are 2cc adapters for various probes. Does anyone have the link to this product?

I have no idea what a 2cc coupler either, but I guess its a bunch of probe wires. I checked my radio shack spl meter and it only output ports, no input ports.

The input port is the big tubelike plastic thing sticking out of the top that you point toward noises. The coupler connects to that and a 2cc one Etymotic makes approximates the human ear so that you could measure the amount of sound that would actually reach the eardrum if you had one of the Etymotic canalphones in.

It isn't on our web site. If you want one you have to call Russ Thoma or myself at Etymotic Research. The 2cc coupler is a standard volume used in measuring hearing aids, and insert earphones. Like it's name implies it is a 2cc volume. We started making some of these cheap silicone ones that slips over the microphone of the Radio Shack meter for quick field testing.

The 2cc coupler doesn't provide a good simulation of the ear, but it is an ANSI and IEC standard. The volume of the ear is about 1.4cc (if I remember correctly). One of the biggest differences is the diameter. Because of its size the 2cc coupler looks like an acoustic short (due to standing waves) at about 8kHz. You can correlate to the ear up to that point. The SPL in the 2cc coupler is about 3.5dB down up to 750 hz. Above 750Hz it is down another 3.5dB/octave.

Don Wilson
Etymotic Research