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Tag Archives: sound

Sound and Hearing loss

earpictureSo what exactly is sound? Well, sound comes from vibrations which produce waves that travel through the air that we breathe in order to reach our ears and be heard. Now inside of the cochlea in our ears are tiny little hairs that are moved by the vibrations in the air. When the vibrations cause the hairs inside of our ears to move, the hairs turn the vibrations into electrical signals that which are then transmitted to our brains in order to make sense of them. Now these tiny hairs inside of our ears are a very delicate and sensitive thing. When the volume of sound gets too loud these hairs can be damaged. When they are damaged from hearing too much noise these hairs fall off. This is what causes hearing loss. As more and more of these hairs fall off the worse your hearing loss becomes. To make things even worse these hairs do not ever grow back once they are gone. This is the reason that hearing damage/loss is permanent and cannot be repaired once the damage has already been done.

So what is a safe level of sound? Well, the answer to this question is surprisingly complex. It is actually possible for any sound that is 85 decibels or higher to cause hearing damage. The other important factor in determining how much sound is too much for your ears is the duration of exposure. It is generally recommended that you have no more than 15 minutes of exposure to sound of 100 decibels. This is roughly the maximum volume of many MP3 players and other portable music devices that we typically use on a day-to-day basis. The louder that the sound gets the less time that it takes to cause hearing loss. Exposure to any sounds of 110 decibels or greater places you at risk of permanent hearing damage with anything longer than 1 minute of exposure.

So what are some simple tests to determine whether or not the sound that you are being exposed to is too much? Your ears will usually give you some warning signs that that the sound that you are hearing is too loud. One general indicator that that noise around you is too loud is that you have to raise your voice to be understood by people that are close by to you. Another obvious sign is that the noise hurts your ears. The threshold for pain is roughly 120 decibels which is as loud as a jet engine at takeoff. A third and somewhat more subtle way to know whether or not the noise is too great is if your ears ring after listening to a sound. This often happens to people after going to loud concerts or possible listening to loud music on headphones for a while.

In the end your hearing is a very precious sense. Once it is gone it is gone forever so if you find yourself in a situation where you are experiencing too much noise take some simple steps to protect yourself. The first way you can protect your ears from noise is to just simply walk away from the loud sound. If you are unable to simply walk away from the excessive noise then you should put earplugs in your ears. Lastly, avoid listening to excessively loud music for long periods of time. We all have to put away our headphones from time to time.

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Timbre: Emotions in Music

Timbre, also called tone color or tone quality, is the quality of a musical note that differentiates different types of sound, such as a trumpet and a guitar. When these two instruments play a note with the same loudness and pitch, they still sound different. That is because the timbre of the instruments is different. Timbre is determined by the physical characteristics of the sound, such as the spectral envelope, the rise, duration, and decay time envelope, the prefix to the sound, micro-intonation, and the range between tonal and noiselike character. Timbre is the quality of a sound that makes it different from others.

Why is it that two singers with the same range, singing the same note, at the same volume, do not sound the same? They might sound similar, but they might sound extremely different. It depends on the physical aspects of that which produces the sound, such as the vocal cords, and the method of delivery. That’s why some people have extraordinarily beautiful voices and some people, frankly, do not.

Timbre is that which makes you cry when you hear a sad song. It is what makes bagpipes so mournful. It is what makes a violin sound so beautifully sad. But it is also what makes the saxophone and flute so joyful. The pitch plays no part in the emotions associated with the sound. The timbre controls that entirely. The method in which these instruments are played also affects how they sound. For instance, the violin can sound incredibly happy and upbeat when played in an Irish folk song. And the flute can sound wistful and lonely when played slowly, with long notes stretching out sorrowfully. All of the emotions we feel when we listen to music come from the tone quality, the timbre.

Here’s an example of the mournful, yet beautiful, bagpipes at work:

And here is an example of very interesting and beautiful timbre in a voice:

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In A Vacuum: Silence

A vacuum is space that contains no matter. Outer space is a vacuum, more or less. We can create artificial vacuums here on earth. The strange thing about a vacuum is that sound cannot travel through it. So, if something big out in space explodes, in a supernova, you can see it, but you will never hear it. If you’re in space, and a bomb goes off near you, you may feel the heat wash over you, but you won’t hear it.

The reason that sound can’t travel in a vacuum is that there aren’t any particles to carry the wave. Sound waves are longitudinal waves that must have a medium to travel through. They cannot transfer energy from particle to particle because they are spaced too far apart, and the energy cannot jump from particle to particle.

Whenever you see a movie that takes place in space, listen to see if they’re following this law of physics. Much of the time, if there’s an explosion, they add sound effects, when in reality it’d be silent. Take the newer Star Trek movie, for example. When people are pulled out into space after part of the ship was destroyed, everything was silent. That is how it should be. Next time you’re watching a space movie, listen intently to your sub and speakers, and see if the filmmakers got it right.

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Defining the Doppler Effect

Have you ever noticed the way sound changes as it passes by you? The sound of a car horn as the car drives past? Notice how the pitch changes? This is what is known as the Doppler Effect.

The frequency of the sound waves determines the pitch. Sound travels at a constant velocity of 340.29 m/s, but since the wavelength of the sound wave can change, so can the frequency. When an object is stationary, the sound waves that emanate from the object all have the same wavelength, and so therefore have the same frequency. But when an object is moving, the wavelengths of the sound waves moving in the same direction as the object shorten, resulting in the a higher frequency. You perceive this as a higher-pitched sound. After the object passes you and begin to move away, the wavelengths lengthen, resulting in a lower frequency and pitch.

The Doppler Effect is the sound of this transition from high to low pitch as a result of the object’s movement. The same concept applies to breaking the sound barrier. When an object moves at 340.29 m/s, it is traveling at the speed of sound. Once it moves faster than the speed of sound, the waves overlap, resulting in constructive interference. This is what creates a sonic boom.

When one begins to understand how sound works, it becomes evident that sound is not always what it seems. Suppose you’re driving, and your favorite song comes on the radio. You begin singing at the top of your lungs, at a note you perceive to be 465 Hz. But a passerby hears the note at 473 Hz. What you perceive to be 465 Hz is as true as the passerby’s perception of it being 473 Hz. The same sound can be perceived in an infinite number of ways, depending on the motion of the object and the one perceiving it. So really, sound comes down to perception.

Of course, only in relation to pitch. The loudness and timbre are not controlled by motion. The speaker controls that.

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Maximizing the sound setup in your listening room


Surround soundIt may seem counterintuitive, but the ultimate goal in properly placing your subwoofer is to create the illusion that it’s not there. The full, rich, big sound should seem like it’s all coming from your speakers. Your subwoofer should be the strong and silent type, while your speakers garner all the glory.

The setup of the sub is critical towards achieving this goal. But don’t worry if you’re not a custom installer. Here are some basic tips for setting up your new sub.

I always recommend experimenting with the placement of the sub. If you have some flexibility, placing it in the corner will usually increase the output by about 6dB. That’s due to what’s called the corner loading effect. But corner placement may also exaggerate your room’s peaks and valleys, so experimentation is still a good idea.

A good place to start is by pinpointing your prime listening position, better known as “the sweet spot”. In layman’s terms, pick your favorite chair or couch spot. Now place your sub in that spot, but not on the floor. It’s best to place it directly on the chair or couch. The idea is to place the sub in the exact location you’ll be sitting most of the time. Now turn on your favorite music, preferably something that’s heavy on the bass.

Now you’re ready to crawl around on the ground to all the locations in the room where you might place the sub. The object here is to identify the spots where the bass sounds the most full and natural. Remember that this isn’t a test of your bass expertise. Sound is subjective and the best spot is going to be the one where the bass sounds the best to your ears. That’s the spot for your sub.

Some additional tips for your listening pleasure

  • Another item to consider is proper output level.  A common tendency is to set the sub volume too loud. The goal here is to integrate the sub into the speaker system so it works seamlessly, producing sound in equal parts throughout the entire frequency range.
  • Keep in mind that hard surfaces are reflective and will generally produce sound that’s a little on the bright side. If you have hardwood floors, an area rug or something soft will help prevent sound reflection by absorbing it and preventing it from bouncing back and “blurring” out other sounds.
  • If your speakers and sub are all small, keep the sub within a few feet of the front left or right speaker. This is so the bass sounds like it’s coming from the speakers, not the sub. If your speakers and sub are fairly large, you have more options for placement.

Does anyone out there have their own personal tips for subwoofer placement? I’d love to hear them!

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