Game Creation with XNA/Audio Sound/Introduction

Introduction

Good sound is a crucial part in a successful game. For this you need to learn about XACT and about ways to creation sound and audio. Also finding free sounds is an important topic.

Sound is a wave form that travels through all types of terrestrial matter (solids, liquids and gases). Humans can hear sound as a result of these waves moving the ear drum, a membrane that, with the help of the middle ear, translates sound in to electrical signals. These signals are sent along nerves to the brain, where they are "heard". We most commonly hear sound waves that have traveled through the air. For example what we call thunder, is the shock wave of a lightning bolt; that is, when lightning strikes, it displaces the air around it sending sound waves in all directions. We can also hear sound in water and through solids. Because of their higher density, sound actually travels farther in these mediums than through the air. Sound, as we normally think of it, usually originates from some sort of movement or vibrating body.

A sound wave with frequency and amplitude labeled.

The frequency of a sound wave, measured in Hertz (Hz), determines the pitch, or how high or low a sound is. It is the distance between peaks in a sound wave. Longer, low frequency wave forms (e.g. bass sounds) travel farther and can travel through different forms of matter more easily than high frequency sound waves. Whales use both high frequency sound waves, including ultrasound and low frequency sound, including infrasound. The loudest and lowest sounds they make, travel the farthest, up to hundreds of miles.

The amplitude or loudness of a sound wave, is measured in decibels (dB) which is a logarithmic scale. A jet engine is frequently said to be around 140 dB, while a blue whale call can be up to 188 dB. Due to the nature of the dB scale, these sounds are millions of times louder than a whisper.

Even very "simple" sounding tones, like that of a flute, are not perfect sine wave forms. Hardware and software based sound generators are able to create sine waves and other wave forms such as triangle (saw) or square waves. In general each perceived, or fundamental tone may have a series of overtones and harmonics.

A more typical sound wave form, taken from a voice recording