Posts Tagged ‘Introduction’

An Introduction to the Properties of Sound for Recording Musicians

An Introduction to the Properties of Sound for Recording Musicians

by Clay Butler

Obviously, if you’re reading this article, you have an interest in recording.   I’m sure you also have some notion as to what sound is.  Sound is what we hear, right?  Well, yes.  But there’s a lot more to sound.  Knowing what sound is and how sound works is the key to getting a quality recording.  Let’s get our feet wet in sound waves (pun intended).

WHAT IS SOUND?

Simply put, sound is Acoustical Energy, or vibration.  More specifically, sound is vibration propagated through a medium, which is then received by our ears and interpreted by our brain as sound.  The reason I say the vibrations are interpreted by our brain as sound is because acoustical energy still exists that we cannot perceive as sound (more on this later).  For example, while a dog might go nuts from hearing a dog whistle, we as humans cannot interpret those vibrations as sound.  Radio, cell phones, Wi-Fi, microwave ovens, and RADAR all use sound waves that we as humans just can’t hear.  So, in essence, when we refer to sound, we really refer to our perception of vibrations.

Sound vibrations that are propagated through the air (or any other medium for that matter) are in the form of transverse waves.  Thus, you could also say that sound is really rapid fluctuations in air pressure.  The vibrations from a vibrating body, such as a guitar string, push and pull on the surrounding air, creating positive and negative pressures.  These waves occur as the molecules of air are slammed closely together as they are pushed by the vibrating body.  The part of the wave consisting of positive pressure, where the air molecules are slammed together, is called a compression.  Negatively pressured parts of the wave, where the air molecules are pulled apart from each other, are called rarefactions.

THE PROPERTIES OF SOUND

How loudly a sound is perceived is determined by how hard the air gets pushed by the vibrating body.  The harder the air gets pushed, the louder the sound.  Although this is typically referred to as volume, in reference to acoustical energy, it is called Sound Pressure Level (SPL).  The scale used to measure Sound Pressure Level is the Decibel scale, or dB SPL (more on the other Decibel scales in a later article).

The pitch of a sound is a function of frequency.   How frequently a vibrating body pushes the air determines how high or low the tone of the sound is perceived.  The more frequently the air gets pushed, the higher the tone of the sound.  As the air gets pushed less frequently, the tone sounds lower.  Therefore frequency is expressed as the number of sound waves occurring over time.  The scale used is known as Hertz (Hz), which signifies the number sound waves per second.  For example, the note “A” below “Middle C” on a piano is 440Hz.

The frequency spectrum is broken up into three parts.  The Audible Range for humans is roughly 20Hz to 20,000Hz (or 20 Kilohertz, abbreviated as KHz).  The frequencies below 20Hz are categorized as Infrasonic.  All frequencies above 20KHz are referred to as Ultrasonic.

ACOUSTICS

Let’s look again at sound being all about our perception.  Generally, we don’t hear the sound emanating directly from its source.  The majority of the time, we hear sound after it bounces off the surrounding walls, along with any other nearby surfaces, and interacts with the room.  We call this acoustics.  Understanding how acoustics influence sound, especially those sounds you’re trying to record, better enables you to get the sound you want without any surprises.  Each time a sound wave is reflected back into an acoustic space, our perception of that wave changes, especially when you hear sound coming directly from a sound source in addition the reflected waves.  This is why it’s not uncommon for a pro recording studio to spend hundreds of thousands of dollars on architectural design and acoustic treatment, so that those extra reflections and wave interference are eliminated.

http://www.claybutlermusic.com

© 2009 Butler Productions

Audio Books Online – an Introduction

When it comes to the endless benefits associated with audio books, this innovative system of entertainment is responsible for a wide-range of accomplishments. The availability of audio books online allow college students to gain a better understanding of a foreign language or other course material. They also equip business professionals with enhanced confidence pertaining to their field. The many different uses for audio books are rather impressive, as a never-ending collection of titles await your curiosity. Before pursuing a particular online site for your source of audio books, consider the following factors:

Extensive Selection of Titles

Number one bestsellers, classic children’s tales, informative how-to’s, and helpful self-improvement titles are just some of the subjects and topics covered in the world of audio books. Thousands upon thousands of possibilities are offered on downloadable and mail order audio book sites, which span an endless selection of titles. Today, millions of people enjoy access to radio dramas, thrillers, comedies, romance, tragedies, and biographies.

Major publishers, such as Harper-Collins, Time Warner, and Simon & Schuster contribute to some of the best-selling audio books on the market. Some audio books even showcase original audio theater presentations hailing from exotic and international locations in the world. There is also no need to look elsewhere for audio books, as the majority of sites dedicated to purchasing and downloading of these materials offer new titles on a daily or weekly basis.

Type of Services

When looking for audio books online, you will encounter a variety of services to consider. Some sites require a subscription in order to gain access to a collection of titles. After joining a membership, an individual then pays a monthly or yearly fee to either download or have audio books sent to their home. Subscriptions to an audio book site is not always required, as some people can simply purchase the titles they want whenever they wish.

Possible Software Installation

Depending on the audio book site you settle on, you may or may not have to download extra software in order to gain access to your selected titles. While some sites require the installation of software, other sites are already compatible with software found on the majority of current computer models.

Audio File Downloads

After you’ve downloaded a selected audio book title to your computer, you will encounter a great deal of flexibility. With this kind of system, you can transfer your audio files to a wide range of media options to maximize portability. Nowadays, audio books are accompanying people on long train rides and road trips; while relaxing in the bedroom; traveling on an airplane; or even washing the dishes.

Some people copy downloadable files to a digital music player. To enjoy an audio book on your iPod, it is required to first burn the file to a CD and then transfer it using iTunes. When burning an audio book to a CD, it is ready for listening on a typical hi-fi or car audio entertainment system. While at work, some individuals enjoy an audio book as they type away on their PC or laptop. A compatible cell phone also accommodates the pleasure of listening to your favorite audio book titles.