Sound

Sound Capture

• We capture, or record, sound by a process called sampling: “measuring” the sound some number of times per second.

• Sampling rate is measured in KHz; 11 KHz to 128 KHz

• Let’s see a simple example

Sound wave

Time

Sound wave

Time

Sample points

Sound wave

Time

Sample points

Sound wave

Time

Sample points

Sound wave

How the sound would play back or output

Time

Sound Characteristics

• Loudness (amplitude)• Tone, high or low (frequency)• Instrument (timbre)• Quality of sound is in the bit depth – much like

color quality in video• 2^8=256 characteristics, 2^16=65,536

characteristics• Single track (monoral) or two (stereo)• CD quality is 44KHz, 16-bit, stereo

Sound Formats

• Pulse Code Modulation (PCM) – developed for phone calls and now called .WAV file type

• Great for sounds, voice and music – but very big files: 4-minute song=40+ MB

• Since we can’t hear all that 44MHz, 16-bit can give us, we compress the file using CODECs: MP3 for example; reduced using a bit rate (28-320Kbps, 128 is CD)

Playing Sounds - MIDI

• Musical Instrument Digital Interface• Hardware dependent – on sound card• Very small files; works for music not voice• FM Synthesis: electronic emulation of

sound – sounds “electronic”• Wave Table Synthesis: recording of actual

instrument samples that are “bent” for tone and timing. Polyphony = number of instruments; 64 to 256.

The Right Sound Card• Always first: What are you going to use it for?• Low-end sound cards lean on processor for

much of the work• 5.1 means five speakers and subwoofer• Recording signal to noise ratio; 40 is poor, 100 is

good• Connectors: (Green) speakers; (blue) line out;

(Pink) microphone; joy stick (15-pin female DB); Michael got it wrong bottom of page 801

• DirectX compatible: Version 9 (or 10?)

Audio Cables

• Used to come with sound card and often proprietary connector(s)

• Cable now comes with optical drive, not sound card

SPDIF

• Sony/Philips Digital Interface connector• Sound card to 5.1 speaker system• Could be “Digital Out”

Speakers

• 2 = Stereo; left and right channels• 2.1 = Stereo plus woofer; probable best

bet.• 5.1 = Six speakers total. Front Left, Front

Right, Front center, rear left, rear right and woofer

• 6.1 and 7.1 systems are now available

Positional Audio

• Uses 5+.1 system to place sound anywhere in 3-D space. Introduced with DirectX-3.

• Creative Labs added to -3 with Environmental Audio Extensions (EAX); rolled into DirectX-8 in 2000

• Dolby Lab’s Dolby Digital used by DVDs, DTS (Digital Theater Systems) use 5.1

On board sound

• If sound is on the motherboard, make sure CMOS has it turned on.

• You will find the sound driver(s) on the motherboard CD

• Card goes into slot (or enabled in CMOS) first, then load drivers

• Make sure connections to speakers is good

Installing a Sound Card

DOSSupport MIDI support

WAV support

Joysticksupport

Drivers, drivers and more drivers

Troubleshooting

• Always make sure the volume is turned up• Make sure you have good connections• Make sure speakers are on – they need

power• Driver problems in Device Manager