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 DOS Support MIDI support WAV support Joystick support 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