11 adding sounds session 7.1. session overview find out how to capture and manipulate sound on a...

11

Adding SoundsSession 7.1

Session Overview

Find out how to capture and manipulate sound on a Windows PC

Show how sound is managed as an item of XNA content

Discover how to create SoundEffect instances and control their playback within an XNA game program

Create an XNA program that implements a drum kit

Chapter 7.1: Adding Sounds 2

Game Idea: “Gamepad Drum Kit”

The idea of this game is to implement a simple drum kit

Each of the buttons on the gamepad will be allocated a different drum type

When the button is pressed that drum sample is played


Computers and Sound

As far as a computer is concerned a sound sample is just another file of data

The computer can run programs that can work with this type of data

Windows Media Player will provide playback of sound data

The Audacity program will playback data and also allow us to capture and manipulate sound


Sound and Computers

Computers work with numbers

A sound is represented by a sequence of numbers, each of which gives the intensity of the sound at a particular instant in time

The above waveform is that for a kick drum


Sound and Compression

To get high-quality sound, a computer needs to sample a sound signal many thousands of times a second

This produces a lot of data

However, some of this data can be discarded because of the way that the human ear works Loud sounds at a particular frequency will

mask quiet sounds at a similar frequency

This is the basis of MP3 (and other) compression


XNA Sound Effects

XNA games can contain “Sound Effect” content

These are sound samples that can be played under program control

These should not be supplied as compressed sound

Instead they should be recorded using the uncompressed WAV format

The WAV format is a standard for “raw” sound samples


Creating Sound Samples Using Audacity

Audacity is a free Open Source program that can be used to edit audio signals

It lets you capture and edit WAV files

You can also add a plug-in to allow the program to work with MP3 files


Using Audacity

You can obtain Audacity from:

http://audacity.sourceforge.net/

Once you have downloaded the program you can also download an install an MP3 plug-in that lets you work with compressed audio files

Remember to respect copyright laws if you use audio files that you did not create


1. Sound Capture


We can capture some sound effects for use in our drums

This in fact turns the gamepad drum machine into a kind of sampler

Sound Content

I have created some sound samples that we can use for the gamepad drum kit

These were recorded using Audacity and then trimmed to the right size


Adding Sound Content

Sound content is added in just the same way as other content

The Content Manager has filters to process audio content

Note that you can only use WAV files to create SoundEffect objects


Browsing for Sound Content

You can add sounds like any other content

Note that you can select multiple items and add them all at once


Sound Content in the Project

Once the content is added it will be made part of the project, as with images

When the project is built and transferred to the target the sound files are sent as well

You can mix images, fonts, and sound effects in the same content folder


The SoundEffect Type

The XNA Framework provides a type which can be used to create sound effects in games

This type is for “spot” effects such as gunshots or explosions

An instance of the SoundEffect type can hold a sound sample and be asked to play that sound

Each XNA device has hardware that allows a number of samples to be played at the same time

The Zune is the most restricted in this respect


Adding SoundEffect Values to the Game World

The sounds that we want to play will be part of the Game World for the Drum Pad game

The sound values will be loaded when the LoadContent method runs

The samples will be played in the Update method


// Game WorldSoundEffect kick;SoundEffect cymbolTing;SoundEffect snare;SoundEffect top;

// Game WorldSoundEffect kick;SoundEffect cymbolTing;SoundEffect snare;SoundEffect top;

Loading SoundEffect Values in LoadContent

The sound effects are loaded into memory along with other content

The SoundEffect version of Load is used for this


protected override void LoadContent(){ // Create a new SpriteBatch spriteBatch = new SpriteBatch(GraphicsDevice);

kick = Content.Load<SoundEffect>("kick"); cymbolTing = Content.Load<SoundEffect>("cymbolTing"); snare = Content.Load<SoundEffect>("snare"); top = Content.Load<SoundEffect>("top");}

protected override void LoadContent(){ // Create a new SpriteBatch spriteBatch = new SpriteBatch(GraphicsDevice);

kick = Content.Load<SoundEffect>("kick"); cymbolTing = Content.Load<SoundEffect>("cymbolTing"); snare = Content.Load<SoundEffect>("snare"); top = Content.Load<SoundEffect>("top");}

Playing Sounds

This is the same edge detection code as before

If button A has been pressed the snare drum sample is played

Once playback has started the sound plays automatically


// test if A has been pressed since the last Updateif (oldpad1.Buttons.A == ButtonState.Released && pad1.Buttons.A == ButtonState.Pressed){ snare.Play();}

// test if A has been pressed since the last Updateif (oldpad1.Buttons.A == ButtonState.Released && pad1.Buttons.A == ButtonState.Pressed){ snare.Play();}

2. Drum Pad


The program loads a sound sample which can then be played using the gamepad

Summary

Computers manage sounds as files of data

The sounds themselves can be held in uncompressed (WAV) format or compressed (MP3 or WMA format)

Sound effects can only be created from uncompressed (WAV) format files

Sounds are managed by XNA as any other content

The SoundEffect type is used to create sound effect variables in the Game World that can be played during a game


True/False Revision Quiz

Sound is held on a computer as a collection of numbers.

When a sound file is compressed all the loud sounds are discarded.

An XNA device can only play one sound effect at a time.

The SoundEffect type manages the playback of sound during a game.

Sound is just another type of XNA content.


11 adding sounds session 7.1. session overview find out how to capture and manipulate sound on a...

Documents

numbersa sound

highquality sound

sound capturechapter

raw sound samples chapter

soundscreating sound

quiet sounds

sound effect contentthese

drum sample