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Michael Green
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PostSubject: understanding audio   Fri Aug 23, 2013 11:14 am

Do we know what audio is?

We can get so wrapped up in this hobby that sometimes we forget what audio is and how it works. We start thininking of name brands and the reputations they develope and replace what we are hearing and how to make it sound good with a plug and play type of mentality. "if I plug this brand into that I will get good sound". But is that all we need to make good sound? Obviously not.

We are at the age of needing to understand audio if we are to raise the level of our listening to what we have called "the absolute sound".

The absolute sound was coined by one of the audiophile pioneers in writing Harry Pearson, and refers to the reproduction of a recorded event. Harry is basically saying that you should be able to reproduce the music in your listening room as accurately as it was originally recorded. Allthough there are debates over what a recording sounds like as far as tonality and size of stage the hobby of listening has blossomed into a dedicated search for uncovering the musical recordings content.

My search is one of finding every note and every piece of recorded signal no matter how big or small and making it exposed as usable content to enjoy. Along this path I have found a great many discoveries and learned much about the signal path and the signal that is to be delivered down that path. I've spent years and years of stripping away the things that get in the way of the recorded signal and have found what the signal needs to be mechanically hosted and moved through the audio pathway. This becomes a tricky adventure at times because I have found the audio signal to be far more sensitive than what the audio industry originally was thinking when making components to play sound, but in the end the music doesn't lie and is waiting for us to unlock the magic of sound reproduction the way it was indeed originally recorded.

For me the study of the signal path and how audio works never ends and the more I learn about how things work on the most minute levels reveals some of the biggest truths. I have found that simplisty is the key to the greatest revolutions and yet within this simplisty we have a whole new hobby waiting for us to explore and uncover. We, when we have the signal at it's most vulnerable state, are able to reproduce an exact copy of the recorded event or many flavors of these events. We are able to go where the hobby has not yet gone as far as the real size and space of these recordings and able to look inside of the true meaning as if we were there in the studio or live hall. Yes it does take work and understanding but when we do get a clance it is hard to not take a deeper look into the original.

analog

Analog audio is a representation of a sound that is analogous to the air pressure waves of the sound. That may sound complicated, but it is actually very easy to understand. Sound is waves of air molecules. Analog audio is a representation of the intensities of those waves in a different form, such as voltages on a wire or magnetized particles on a tape.

The Basics of Sound

Sound is nothing more than the movement of air and it's reactions to what that air movement vibrates. For example, the sound of a firecracker going off is actually an experience of shock waves that move through the air due to the rapid expansion of the firecracker. The firecracker expands, the molecules of air get pushed towards you, your ears sense the movement of the air molecules and your brain interprets that as sound. When the air molecules move, there are points in the wave when they are all bunched up together (this is high pressure) and there are points when there are relatively few air molecules (this is low pressure). Air pressure reacts differently in every environment based on the conditions of the air hosting the sound.

I say high and low pressure to represent movement and paint the picture of less or more. Why? It's important to think of audio as moving in a state of and within the laws of nature. In nature there are no empty holes. If something is pushing forward it is also pulling back through the means of fair exchange.


How Sound Is Recorded

Perhaps the easiest way to understand how sounds are recorded is to imagine Thomas Edison's phonograph, the first recording device. To record the sound of a voice, the user would speak into a large horn, at the back of which was a diaphragm (a sheet of flexible material). The diaphragm was connected to a needle, which was placed against a rotating tinfoil cylinder. This is how it worked: The user's vocal cords vibrated and pushed air towards the diaphragm. The flexible diaphragm vibrated, causing the needle to move and scratch a groove in the tinfoil cylinder. To play back the sound, the user just reversed the process: The tinfoil cylinder was rotated, causing the groove to vibrate the needle. The needle then vibrated the diaphragm, which pushed air in the exact same manner as the original voice had.


Analog Audio

To record analog audio of a sound today, we use a microphone, which has a diaphragm just like the one in Edison's phonograph. Only this time, the diaphragm is not hooked up to a needle. Instead, the diaphragm in a microphone is connected to a device called a transducer. When the diaphragm is vibrated by the sound of a voice, the transducer converts those vibrations into electrical energy. The portions of the sound that are high pressure cause the transducer to create positive voltage, and the portions of the sound that are low pressure cause the transducer to create negative voltage.


Converting the Voltages Back to Sound

So how do we convert those voltages back to sound? We simply reverse the process, just like we did with Edison's phonograph. We can imagine those negative and positive voltages as waves moving down the microphone's cable. Those waves travel through the wire until they reach a speaker, which is also a type of transducer. This time the transducer converts the electrical energy back to acoustical energy (sound). When positive voltages reach the transducer, the diaphragm in the speaker causes a lot of air to move (high pressure). When negative voltages reach the transducer, the diaphragm pushes less air (low pressure). The process the speaker goes through is the reverse of the process the microphone goes through.


Analog Recordings

Recall that Edison's medium for storing an audio recording was a tinfoil cylinder. The grooves on the cylinder were a representation of the sound that created them. A tape recording is a representation of sound that is in the form of magnetic particles arranged along a strip of tape. A vinyl record is a representation of sound that is in the form of grooves on a disc. A tape player and a record player simply convert those representations into electrical energy, which passes through the speaker wire to the speaker's transducer, which converts the electrical waves back to sound.

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