1. Audio Interfacing

This chapter concentrates on a computer’s onboard audio capabilities, because the same concepts translate to more sophisticated (and higher-performance) audio interfaces. Note that there are many brands and models of audio interfaces, making universally applicable lessons impossible. As a result, multiple sidebars in this chapter explain audio interface characteristics to provide important background information.

Several lessons in this chapter are divided into versions for Macintosh and Windows computers. You won’t need to read the Windows-specific lessons if you use a Mac, and vice versa. However, all users should read the sidebars, because they cover information that’s applicable to both platforms.

To make the best use of the lessons in this chapter, you’ll need the following:

• An audio source, such as a portable music player (iPod, iPhone, Android, CD, etc.) with a 1/8-inch minijack output, or other device with a suitable adapter to provide a 1/8-inch minijack output. Laptops may also have an internal microphone you can use; however, using a line-level device is recommended, and the lessons will reference that type of input. You can also use USB microphones that plug directly into a computer’s USB port; however, note that they may introduce significant latency, as described later in this chapter, when used as class-compliant devices with Windows computers.

• Patch cable with a male-to-male 1/8-inch plug to connect the audio source to your computer’s audio input jack.

• Your computer’s internal speakers for monitoring or earbuds/headphones with a 1/8-inch stereo plug suitable for plugging into your computer’s stereo output. You can also patch the output to a monitoring system if you have suitable cables.

1. Connect the audio source to the Mac’s 1/8-inch line input jack via the 1/8-inch patch cord. If you’re not using internal speakers, plug the earbuds/headphones or monitoring system input into the Mac’s line-level output or headphones jack.

2. Open Audition and choose Audition > Preferences > Audio Hardware.

3. Don’t change the Device Class or Master Clock preferences, because they will default correctly. The Default Input drop-down menu lists all available audio inputs. Choose Built-In Line Input.

4. The Default Output drop-down menu lists all available audio outputs. If you’re using the built-in speaker, choose Built-In Output; for the line-level output, choose Built-In Line Output.

5. I/O Buffer Size determines the system latency. (See the sidebar “About latency [computer-based delay] for more information.) Low values result in less delay through the system, whereas higher values increase stability. A value of 512 samples is a good compromise.

6. In the Sample Rate drop-down menu, choose 44100, which is the standard for CDs. The Sample Rate drop-down menu lists all available sample rates. For most Macs, the choices are 44100, 48000, 88200, and 96000kHz. (In theory, higher sample rates improve fidelity, but the difference is subtle at best.) Windows computers and external audio interfaces generally offer a wider choice of sample rates.

7. Click Settings to open the Mac OS Audio/MIDI Setup dialog box, and then click Built-in Line Input.

The settings will mimic what you set in Preferences (e.g., if you selected a 44.1kHz sample rate, this will appear as the sample rate in the Format field).

8. In the other Format field, choose 2-channel, 24-bit, which specifies Bit Resolution. All Mac OS X audio-related parameters are now set.

9. Close the Audio Devices dialog box, and click OK in Audition’s Preferences dialog box.

10. Choose Audition > Preferences > Audio Channel Mapping to correlate Audition’s channels to the hardware inputs and outputs. For example, Audition’s 1(L) channel will be mapped to Built-in Output 1. Click OK to close this dialog box.

The next sections relate to the Windows setup, so proceed to the section “Testing inputs and outputs with Audition (Mac or Windows).”

Unfortunately, ASIO is not part of the Windows operating system, so for these lessons you’ll use the MME (Multimedia Extensions) protocol. It has relatively high latency but is stable and predictable. Experienced computer users can download the general-purpose ASIO driver ASIO4ALL, which is available free of charge from www.asio4all.com. It is the de facto ASIO driver for laptop owners who want to use ASIO with internal sound chips. Although you’ll use MME for now, with a professional audio interface, use the ASIO or WDM/KS drivers provided with it, or as an alternative, ASIO4ALL.

1. Windows motherboards typically have mic and 1/8-inch line inputs. Connect the audio source to the computer’s 1/8-inch line input jack via the 1/8-inch patch cord.

2. If you’re not using internal speakers, plug the earbuds/headphones or monitoring system input into the computer’s line-level output.

1. In Windows 7, choose Start > Control Panel, and then in the Control panel double-click the Sound icon. With Windows 8, press the Windows key+X, choose Control Panel, and click the Sound icon.

2. Click the Playback tab. Click either Speakers or Headphones, depending on what you have plugged into the computer’s output jack. After clicking the appropriate choice, click the Set Default button to make this your default audio output.

3. Click the Sound dialog box’s Recording tab.

4. Click Line In, and then click Set Default. Click the Sounds tab, and for Sound Scheme, choose No Sounds. It’s distracting to hear system sounds while you’re working with audio. Click OK.

1. Open Audition, and choose Edit > Preferences > Audio Hardware.

2. From the Device Class drop-down menu, choose MME.

3. From the Default Input drop-down menu, choose the default input device (Line In) you specified previously; from the Default Output drop-down menu, choose the default output device (Speaker or Headphones) you specified previously. Do not change the Master Clock preference.

4. Choose a latency value of 200ms, which is a “safe” value for most computers. Latency determines the delay audio experiences as it passes through the computer. Low values result in less delay through the system, whereas high values increase stability.

5. In the Sample Rate drop-down menu, choose 44100 (in theory, higher sample rates improve fidelity, although few people can hear a difference). The Sample Rate menu lists all available sample rates. Most Windows internal audio chips offer a wide variety of sample rates, often from 6000Hz to 192000Hz. External audio interfaces typically offer fewer options that are intended for professional audio and video projects. After selecting the Sample Rate, click OK.

6. Choose Edit > Preferences > Audio Channel Mapping to correlate Audition’s channels to the hardware inputs and outputs. For example, Audition’s 1(L) channel will be mapped to Line 1. Click OK to close this dialog box.

1. Choose File > New > Audio File to create a new file in the Waveform Editor. A dialog box appears.

2. Name the file. The sample rate should default to the value you selected in Preferences.

3. Choose the number of channels. Their inputs will default to what you specified in Preferences. If you choose Mono, only the first channel of the input channel pair will be recorded.

4. The bit depth represents the project’s internal bit depth, not the bit resolution of your interface’s converters. This resolution will be used to calculate changes in volume, effects, and the like, so choose the highest resolution, which is 32 (float).

5. Click OK to close the dialog box.

6. Click the Transport Record button, and then start playback from your audio source. If all connections are defined and all levels are set properly, you’ll see a waveform being drawn in the Waveform Editor window. Record several seconds of audio.

7. Click the Move Playhead to Previous button in the Transport, or drag the playhead (also called the current time indicator [CTI]) back to the beginning of the file. Click Play, and you should hear what you recorded in your chosen output device (internal speakers, earbuds, headphones, or monitoring system). Click the Transport Stop button to end playback.

8. Now test recording and playback in the Multitrack Editor. Choose File > New > Multitrack session. A dialog box appears.

9. Name the file. For template, choose None. The sample rate should default to the value you selected in Preferences.

10. As with the Waveform Editor, choose the highest resolution of 32 (float), and then choose the number of output channels (Stereo) for the Master Track.

11. Click OK to close the dialog box.

12. Arm a track by clicking the R (Record) button. Start playing your audio source; the channel’s meter should indicate a signal. Note that the input will connect automatically to the default input; however, if you click the input field’s right arrow, you can choose just one input for mono tracks or you can open the hardware section under Preferences if you have a multi-input audio interface and want to choose an input other than the default.

13. Click the Transport Record button. If all connections are defined and all levels are set properly, you’ll see a waveform being drawn in the Multitrack Editor window. Record several seconds of audio.

14. Click the Transport Move Playhead to Previous button, or drag the playhead back to the beginning of the file. Click Play, and you should hear what you recorded in your chosen output device (internal speakers, earbuds, headphones, or monitoring system). Click the Transport Stop button to end playback.

• Professional interfaces usually have capabilities beyond those offered by internal audio I/O and therefore have their own control panels for routing signals, controlling levels, and the like.

• Interfaces often have more than one set of stereo inputs and outputs. When you’re choosing default inputs and outputs, you’ll have a much wider selection compared to using a computer’s internal sound capabilities.

• With interfaces that provide various connections (USB, FireWire, Thunderbolt, etc.), try them all on extended sessions to determine if one option works better than the other.

• Windows USB interfaces can be class-compliant, meaning they don’t need custom drivers. However, always use the custom ASIO or WDM drivers provided with an interface for maximum functionality and minimum latency.

• With Windows computers, never use drivers called “emulated,” such as “ASIO (emulated).” These result in the worst performance of all possible drivers.

• Some interfaces include a feature called zero-latency monitoring. This means the input can be mixed directly to the output, and the mixing is typically controlled by using an applet that appears onscreen to bypass any latency caused by going through the computer.

• With ASIO interfaces, Audition will default to monopolizing any sound capabilities. To access the ASIO interface in other applications that are running, choose Preferences > Audio Hardware, and select the “Release ASIO driver in background” check box in the dialog box. Giving the other application the focus will allow it use the ASIO interface, unless Audition is recording.

2. What is an unavoidable, negative by-product of working with computer-based audio?

3. How can you minimize latency?

4. What are the advantages and disadvantages of high sample rates and high bit resolutions?

5. Although many external audio interfaces include ASIO drivers, the Windows operating system does not. How can you use ASIO with laptop sound chips?

2. System latency causes a time delay between the output and what’s being recorded at the input.

3. Change the number of sample buffers to alter latency. Using the smallest number possible, consistent with the audio not producing clicks or pops, provides minimum latency.

4. High sample rates and bit resolutions have the potential to deliver better audio quality but create larger audio files and stress the computer more than lower rates and resolutions.

5. The free driver software, ASIO4ALL, provides ASIO drivers for sound hardware that was not designed for ASIO compatibility.