Before girlfriend start

Objectives: Learn what is sound card, exactly how does the work, different audio technologies that the utilizes, and which connectors have the right to it have.

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Prerequisites: no prerequisites.

Key terms: audio, digital, analog, sample, wave, channel, standard, dolby, bit, hz, connector, interface

Sound Waves

The task of a sound map in a PC mechanism is to transform digital data from the PC right into analog audio that have the right to be reproduced top top speakers. The ingredient which does this is referred to as the Digital to Analog Converter (DAC). To input sound to our computer we have to transform analog sound come the digital sound. The ingredient which go this is referred to as the Analog come Digital Converter (ADC). An additional component the the sound card which participates in the whole procedure is the Digital Signal Processor (DSP). DSP is an on-board processor the reduces the CPU load. To know all this we first need come know just how sound tide work. Sound waves room propagated v the air utilizing compression waves. In ~ the origin the sound wave is produced by compressing and also uncompressing the air. Natural sound wave is one analog wave. When we’re handling an analog tide we must be aware of two things that describe it. The very first is the frequency. The frequency is the distance in between the top (peaks) or the valleys the the wave.



Image 324.1 – Frequency

The 2nd thing is the amplitude or volume. Amplitude is the total height the the wave.



Image 324.2 – Amplitude

The point is, PCs address digital signals. In order to produce or record a sound wave through a computer we have to take analog wave and represent it digitally. To carry out that we have to sample it. That means that we take a look in ~ the tide at some suggest and keep in mind the amplitude and also the frequency that the tide at that specific point. We execute that trough the totality wave on numerous points. By doing that we develop a digital approximation of the analog wave.

Bits per Sample

When we room sampling sound tide there’s two different parameters the we must keep in mind. The an initial one is the number of bits of memory offered to stand for a given sample (bits per sample). The more bits we use to stand for a provided sample the closer digital sample almost right the analog wave. Because that example, us can create an eight bit sample of the wave at any kind of given point. If we use 8 bits us can gain 256 different decimal numbers (2 to the strength of 9) to stand for a certain sample. The selection starts native 0, so we have actually numbers native 0 come 255. Those space the numbers that have the right to be offered in decimal type to represent the sample. If we usage 16 bits to stand for the sample, we have up come 65536 feasible values to represent the tide at any given point (2 to the strength of 16). Keep in mind that values start from zero so the selection is native 0 come 65535. If us go further, the 20 bit sound cards usage a sampling size of 1048576, 24 bit sound cards usage a sampling size of 16777216, 32 bit sound cards usage a sampling dimension of 4294967296, etc.

Sampling Rate

The second parameter we need to keep in mind once converting analog come digital tide is the sampling rate. The sampling price is the variety of times per second that a sample is taken (the variety of analog signal samples taken over a period of time). The much more samples we take per second the closer the digital tide is to the analog wave. Sample rates are expressed in cycles every second, dubbed hertz. Because that example, sampling rate can be 1000 hertz (Hz) i m sorry is 1 kilohertz (kHz). For example if we usage 8 kilohertz sampling rate, the sound top quality would be really bad, it would certainly sound choose a phone call connection. In reality 8 kHz is sufficient for phone call conversation since the human being voice range is around 4 kHz, however for computer audio this is not nearly enough. 22 kHz is the radio quality. The 44 kHz is the sample price that have the right to reproduce the audio frequencies up to 20,500 hertz, i m sorry covers the full selection of person hearing. 44 kHz is considered CD quality. 48 kHz is offered in Digital TVs and also DVD movies. 96 kHz is provided in DVD audio. 192 kHz is used by LPCM (Linear Pulse code Modulation) which is a DVD-music production format. It is likewise used in BD-ROM (Blu-ray Disc-ROM) and HD-DVD (High-Density-DVD), which are two optical disc styles providing HD video clip and high density data storage. Higher sample rates also require more bits of data every sample (more memory). Because that example, to have actually CD top quality audio we likewise have to use 16 bits every sample.

Audio document Size

We can sample the wave an ext frequently however the downside with this is the the digital papers that we create using higher sampling rate and an ext bits every sample, gain really big. That’s because we use much more samples and more memory to store those samples. Because of that various compression schemes have been developed to mitigate the size of digital audio files maintaining the fidelity of the initial sound indigenous the greater sampling rate. For instance we have actually MPEG files, Microsoft windows Media Files, advanced Audio Coding, etc. These schemes use various species of compression come shrink the dimension of digital files. As soon as talking about audio formats we should point out the there major groups that audio file formats. We have uncompressed audio formats, such as WAV (Windows standard), AIFF (Audio Interchange file Format, the Macintosh tantamount of the WAV), AU or life header-less PCM (UNIX standard, sustained by most net browsers). Next, us have styles with lossless compression, such together FLAC, Monkey’s Audio (APE), WavPack (WV), TTA, ATRAC advanced Lossless, to apologize Lossless (m4a), MPEG-4 SLS, MPEG-4 ALS, MPEG-4 DST, home windows Media Audio Lossless (WMA Lossless), and Shorten (SHN). In the end, us have styles with lossy compression, such as MP3 (MPEG-1 class 3), Vorbis, Musepack, AAC (Advanced Audio Coding, likewise known together MPEG-2), ATRAC, home windows Media Audio Lossy (WMA lossy), RA or RM (Real Networks, developed for streaming audio files).

Sound card Considerations


A an easy sound map will have actually analog speaker-out jack and an analog microphone jack. This allows us come send audio the end to the speakers, too as input audio v the microphone. Keep in mind the the speaker-out signal is magnified and the the computer system controls the sound level the is sent. Some cards will also have a line-out connector, which is supplied to send audio to various other sound devices. Store in mind that the line-out signal is unamplified. Most sound cards will additionally have a line-in connector which allows us to pull audio from other sound tools (CD players, musical instruments, etc) and also bring to our computer to document it, manipulate the or just play it on ours PC. All interfaces mentioned so much are analog, and a huge number of gadgets will usage them. However, newer devices can process digital audio signals. Consumer standard for digital audio transport is S/PDIF, which stands for Sony/Phillips Digital Interface. It’s offered to carry digital documents from one device to another, without having actually to go through a digital to analog and analog come digital conversion. Instead of that the sound is moved digitally. Part sound cards also have a Midi/joystick port, i m sorry we usage to affix a game controller come our computer or to user interface with Midi sound devices. Part sound cards will also include HDMI ports.

Number of Channels

Different sound cards will usage different variety of channels. Channels can do sound an ext realistic. Simple sound cards will have 2 channels, i m sorry isstereo audio. Typical radio and also TV have stereo sound. Really old sound cards actually had actually one channel (mono sound), however today all sound cards will have at the very least two channels. We can also purchase a 4 channel stereotype audio card, which gives us prior left, front right, rear left and rear right channel. 4 channel audio is quadraphonic audio, and it is very early attempt that surround sound. Higher top quality sound cards will additionally implement Dolby Digital Sound. Dolby Digital is a digital audio coding technique that to reduce the amount of data essential to produce high quality sound. It additionally reduces noise coming through the system. Dolby Audio gives 5 full bandwidth networks (also dubbed audio channels), which space front left, former right, center, surround left and surround right. Dolby Digital likewise includes one low bandwidth channel referred to as the short Frequency impact or LFE channel (also called the subwoofer channel or results channel). Together, this Dolby Digital traditional is called Dolby 5.1 since we have five full bandwidth channels, and one LFE channel. All channels are delivered on 6 strategically put speakers. There are various other Dolby Digital implementations like the Dolby Digital 6.1 and also Dolby Digital 7.1. The 6.1 and 7.1 variation of Dolby Digital add an ext channels. Because that example, 6.1 has actually 6 audio channels and 1 effects channel. 7.1 has 7 audio channels and 1 results channel.

Other Features

Some sound cards will support Digital Theater device or DTS standard. This conventional is draft to produce near theater top quality audio indigenous your pc system. It has actually 6 channels and it’s based upon Dolby 5.1. In stimulate to produce DTS sound we additionally have to have a DTS compatible speakers. Part sound cards will assistance the EAX Standard. The EAX conventional is design to produce interactive 3D audio in computer gaming. There is also a THX conventional which is a a sound high quality standard, originally developed for film, yet now it is available on sound cards. Some cards will support MIDI (Musical instrument Digital Interface). This is a protocol for recording and playing audio produced on digital synthesizers.


Almost every sound cards will have ports which accept 3.5 mm plugs because that analog input and output. We contact those harbor Mini TRS ports. The number of Mini TRS ports will depend on the variety of speaker channels, microphone or heat in support, etc. Mini TRS use standardized color coding i beg your pardon can assist us recognize the suitable port. For example, Mic-in is pink, line-in is blue, and line-out is green (front speakers). We can also have various other colors. For example black harbor is commonly for behind speakers, and orange is for center and also surround speakers.


Image 324.3 – Mini TRS Ports


Image 324.4 – Mini TRS male Plug (3.5 mm)

Although these colors space standard, we have to consult the sound map documentation for certain details. Over there is also a Toslink connector which is used with digital optical input/output, because that S/PDIF audio.


Image 324.5 – TOSLINK masculine Plug

We additionally have an RCA connector i beg your pardon is usually offered for coaxial digital entry or calculation for S/PDIF audio. It can be supplied for analog audio, but RCA connector top top a sound card is usually used for S/PDIF digital audio.



Image 324.5 – RCA male Plug

A DB-15 connector top top a sound map is supplied to connect to MIDI devices or video game joysticks. Occasionally it is referred to as a video game port.


Image 324.6 – MIDI/Game Port

A sound card v an HDMI port is qualified of sending HD audio come an HDMI device.

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Image 324.7 – HDMI Port


The sound card converts an analog signal to a digital signal (for example from microphone) or a digital signal to an analog signal (sent from computer to speakers). When we space sampling sound tide there’s two different parameters that we have to keep in mind. The an initial one is the number of bits the memory supplied to stand for a given sample (bits per sample). The 2nd parameter is the sampling rate. Using higher sampling rate and more bits every sample means far better audio quality, however it also method bigger audio files. Various sound cards will usage different variety of channels. Usual connectors which have the right to be discovered on sound cards space Mini TRS, TOSLINK, RCA, DB-15, and HDMI.