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Portable Audio: Safe Listening Out of the Box
Smartphones, PDAs, tablets, portable music players and game consoles have all revolutionized the way we listen to music. These portable devices can store thousands of songs, and in some cases access the Internet, providing a virtually unlimited on-the-go soundtrack for our lives.
But as earbud and headphone listening has become more popular, we're seeing more reported incidents of hearing loss caused by listening to excessively loud music. And increasingly, the aural damage is starting at a younger age. So we did a lot of research and talked to an audiologist. He helped us come up with some practical listening tactics so you can get the most out of your portable player while protecting your hearing — and all without compromising your listening experience.
How loud music leads to hearing loss
We've all been told repeatedly by parents and others that loud music damages our ears. And some of us believe that as long as our eardrums don't rupture, we're OK. But the real business of translating vibrations into what our brains understand as sound takes place behind the eardrum, in the inner ear. Read on for the straight story on how hearing loss happens.
Ground zero in your ear
Behind the eardrum is the inner ear. This is where the cochlea reacts to the vibrations transmitted by the tiny bones of the inner ear and converts them to signals that go directly to the brain.
Only the size of your pinkie's fingernail, the spiral-shaped cochlea is lined with over 30 thousand microscopic hairs. These extremely sensitive hairs are grouped in bundles, arranged in two rows, or bands.
|The delicate hairs of the cochlea are where hearing damage from excessively loud volume levels occurs.|
Each bundle detects a different pitch. The hair cells in the outer band, in addition to detecting sound, act as amplifiers to boost softer sounds to the inner hair cell band, which transmits the information to the brain.
Think of it as a piano keyboard wrapped up inside a snail shell. The highest pitched keys start at the opening, with the lower keys traveling on up into the recesses of the shell. The keys near the opening are exposed to the elements, so they're the most susceptible to damage.
Hearing — the non-renewable resource
At normal volume levels, the sensitive hairs in the cochlea wave back and forth, relaying information on to the brain. Excessively loud sounds hit these hair cells like a tidal wave crashing into a coastal forest — basically, hair cells break and their nerve connections get damaged. Extended exposure makes it worse. In fact, only three hours of too-loud headphone listening can be more harmful than exposure to the sound of an explosion at close range.
So what's the effect on hearing? Well, not only are these hair cells fragile, but they don't repair themselves when damaged. So when a band of hair cells are bent or broken, the ear permanently loses some of its ability to hear that particular frequency. Further exposure increases this loss. Also, once you lose a significant number of outer hair cells, hearing soft sounds of any pitch becomes very difficult as well. In some cases, the volume required to hear anything at all may be so loud that it in turn causes further damage.
The good news
This type of hearing loss from noise exposure — known as acoustic trauma — is usually preventable. You can safeguard your hearing by making a few simple changes in how you use your portable player — without sacrificing the enjoyment and impact of your music.
Limit sound at the source
The simplest solution is to keep the volume of your portable player turned down. While virtually all players come with a printed warning about listening at dangerous levels, some help you do something about it by including a volume limiter.
A limiter lets you lower the maximum volume level of your player so you can't accidentally boost it too high. This can also be a great help for parents to ensure their children listen to their portable players at safe levels.
A good rule of thumb when setting levels is to aim somewhere between one-half and two-thirds maximum volume. Remember that volume levels can vary from recording to recording, and some musical genres have a more tightly compressed — and therefore louder — sound. When checking your level settings, make sure to use a song that has the same volume as most of your music.
If you're thinking, "I won't be able to hear my music clearly if I turn the volume down more," then read on. We've also got ideas to help you get crisper music at lower volume levels.
Bigger files, better sound
There's a trade-off between file size and sound quality. Stuffing your portable player full of as many songs as possible can give you thousands of tunes to listen to, but at a cost. When you import a CD track, your music software program converts it to a sound file of a particular resolution, usually measured in kilobytes per second (Kbps). The lower the resolution, the smaller the resulting file — and the more detail lost.
Music with little detail tends to sound muddy. Most of us intuitively turn up such music in an effort to hear the missing details, and expose our ears to dangerously high volume levels in the process.
The software programs most portables players use, such as Apple's iTunes® or Windows Media Player, have default settings that determine what kind of file incoming music is converted to, and at what resolution.
Songs ripped from CDs are often compressed to 128 kilobytes per second (Kbps) MP3 files (although 256 Kbps is slowly becoming the norm). In the process of compressing the file, much of the audio information is discarded, leaving a general outline of the song. A lot of the sonic detail that gives the music its character can either disappear or sound duller as a result.
|This chart shows the relative file sizes of the same three-minute song saved in different formats, starting with the original CD track on the left. The smaller the file, the more sonic information is lost.|
Switching the import default setting to a higher resolution, or using a different kind of file such as lossless compression format like FLAC, addresses that issue. A 192 kbps MP3 file can approach the sound of the original CD, although there's still some information lost in the compression. A lossless format, however, compresses the file and retains the original information. With a lossless track, you'll hear the original depth and detail of the music.
Generally, a lossless file is about ten times bigger than a 128 kbps low-resolution MP3 file of the same song. This means you can fit fewer lossless files on your player than low-res MP3, but there's a plus: you'll have significantly better-sounding music that can pack a greater punch at a lower — and safer — volume level.
Changing the default import setting on your music manager program is usually pretty simple. In iTunes®, for example, just go to "Preferences" and select "Import Settings." Follow the simple instructions to select a higher bit rate. For Windows Media Player, go to "Options" and select the "Rip Music" tab. You'll see a pull-down menu with your import format options.
It all comes down to the headphones
The tips you just read can get you started, but one of the best ways to enjoy safe and high-quality listening is to get the right headphones. Most earbud headphones included with portable players sit on the outside of the ear canal. Ambient sound slips in through the gap between the earbud and the ear canal, interfering with the sound from the headphones — the sound you want to hear. It's a natural impulse to drown out this unwanted noise by cranking up your music, but this can easily result in dangerously high volume levels. Here are some suggestions on how to avoid that situation.
|Earbud headphones let ambient noise (red) into the ear canal, where it interferes with the sound coming from the headphones (green).|
Seal the sound out, seal the sound in with in-the-ear headphones
In-the-ear headphones position their drivers inside the ear canal. The earpiece is surrounded by a soft sleeve, usually of foam, rubber, or silicone. These sleeves are replaceable, and almost all brands of in-the-ear headphones come with various sleeves to ensure a snug and comfortable fit for different-sized ears.
|In-ear headphones act as a barrier, sealing out external noise (red). The headphone sleeves also help keep the sound you want to hear (green) inside the ear canal, maintaining sound intensity and eliminating the need to turn up the volume.|
In addition to holding the headphones in place, these sleeves also block most of the ambient sound. As a result, your music can pack the same punch at a much lower — and safer — volume level. The sleeves also seal in the sound waves from your headphones, keeping them from losing any intensity by bouncing out of the ear canal. You'll need less volume to give your music presence.
Enclose the ear for protection with around-the-ear headphones
Although in-the-ear headphones are most effective in diminishing external sounds, not everyone's comfortable with 'phones that rest inside their ear canals. Around-the-ear headphones offer a good alternative, with padded earcups that completely surround the ear, and help to minimize external sounds. As with in-the-ear models, the lessening of ambient sounds lets you enjoy your music at lower volume levels.
|Around-ear headphones also help minimize external noise (red), while keeping your ear canal open.|
You can even find noise-canceling models that actively combat ambient sound. These kinds of headphones are generally better at minimizing stable-pitched sounds, such as airplane engine roar, rather than irregular sounds, such as conversations around you.
Be aware of what's around you with on-the-ear headphones
The earbud headphones that come with portable players have their uses, too. Because they don't fully cover the ear canal, ambient sounds are more in the foreground. Sometimes that can be a good thing. If you're running or power walking, for example, being able to hear the sounds around you can help keep you safe. That's all the more reason to protect yourself and your ears, by leaving the volume a little lower when using these kinds of headphones.
Quality you can hear
Regardless of which style you prefer, using better quality headphones can also make a difference. Higher-end headphones have wider frequency response, which means you'll hear more bass and crisper highs. Usually the mid-range will sound fuller, too.
Better sound quality also means you don't have to max out the volume just to hear the instruments playing. As with higher-resolution sound files, you'll be able to listen at safer, lower volume levels and still get the full enjoyment out of your music. And with a little care, you'll be able to do so for years to come.
Special thanks to Audiology Associates of Harrisonburg, Virginia for providing technical information for this article.