An audio signal is simply a digital representation of sound, usually using some changing sequence of binary digits for digital audio signals or an unstable phase shift for audio signals which have a high frequency. The term “frequency” is used to describe the overall” amplitude” of the audio signal. In other words, the higher the frequency, the softer the sound.
Audio latency is the delay that audio implements in the audio interface to hear the audio signal as soon as the input events happen. Latencies range from a few milliseconds to several hundred milliseconds. Latencies are related to the speed of the audio data and the timing required for the audio to reach the user’s ears. For example, suppose there is a Speak/Sleep button on your PC, and you press the button when you are typing in a document. In that case, your computer should be able to wake up when the key is pressed and play the audio automatically when your mouse pointer moves above the keyboard.
Most computers that come with audio interfaces have what are called USB ports. These are usually used for connecting peripheral devices like printers or scanners to the PC. However, there are now new types of audio interfaces with a USB port used for the PC. In addition to making your computer more versatile, these new types of audio interfaces with USB ports allow more excellent compatibility and accessibility. For example, most modern iPods have a USB port that lets you use your iPod with your computer. Many new computer speakers also have a connection called Optical Digital Interfaces (ODI) that allows you to use your computer speaker with your home stereo system.
Inputs and Outputs
Most computer systems have four main inputs and three outputs. The audio interface with the computer will usually consist of four channels: left, right, and center. There may also be six inputs and three outputs, but these are not typical. Other audio interfaces have additional features like extra faders to bring up extra faders for monitor input and output controls and can include optical and coaxial outputs. However, with most systems, only one front panel controls which control speaker output and fader levels. Most other controls are on the front panel of the unit.
2 Channel Outputs
Outputs will usually consist of two channels – one for the audio input and one for the monitor. Many interfaces with computer speakers connect their outputs to line-level outputs using RCA connectors. There are still other types of outputs, including digital and hybrid. Digital outputs are very popular for recording purposes as they do not degrade when sending audio to a tape recorder. Hybrid outputs are used with some software packages as they combine the Line Out and the Line In (stereo) functionality. It is advisable to connect a high-end audio interface with outs to an amplifier to get a sound quality recording.
5 Elements of a Midi Interface
A midi interface usually consists of five elements – an audio interface itself, a midi controller, sample & buffer, and phantom power. The midi controller controls how the signal is processed and how it is sent to the other elements. The buffering buffer is responsible for taking the complete signal and converting it to a constant voltage. The final element, the phantom power, is what powers your audio interface once all of its functions are working. The buffering buffer should not be overdone, as this can lead to distorted sounds. Phantom power is vital and is an essential part of any midi interface.
The latency you hear during playback is directly related to how far away the speaker is from your audio interface. Speakers with higher latencies will send audio to your computer at higher volumes, so the computer has to compensate by sending more commands per second. This results in a much higher amount of delay in the signal, making it difficult to understand or discriminate.
Most audio interfaces work well when recorded in isolation with a monitor pointing towards the recording source. However, suppose you are using the audio interface as part of a recording or mixing process. In that case, you will need to refer to the manual for the particular application to get the best performance. Most applications recommend limiting the number of channels using an external device, but this is easily accommodated using midi controls.