INFO: Chronos as a Sound Output Device [24493]

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Chronos

Detail

Chronos and Sound
One of Chronos’ primary functions is as a sound output device. The main benefit of utilizing Chronos as a Sound Output Device is to reduce variability in Sound Onset Latency between computers. Chronos allows you to consistently present audio with millisecond precision regardless of which device it is attached to.  

Chronos as a sound output device has several options for playing audio, the default of which (called MixMode1) is able to play sound with 1ms of Sound Onset Latency consistently.

Image 1 Chronos audio out and audio in (speakers not included)

Image 2. Chronos audio inputs.

Chronos and Sound Onset Latency
The main benefit of audio presentation with Chronos is specifically in the area of Sound Onset Latency. Chronos comes with an on-board sound card. This allows the sound card, sound card drivers and API to all be controlled in one place. The benefit of this that Chronos will maintain this consistent Sound Onset Latency regardless of the computer into which it is plugged. This then removes the possible confounding factor of Sound Onset Latency variability per computer.

As a check, Chronos allows the user to log the Sound Onset Latency of any sound that is presented through it. To do this, you will first need to log the OnsetTime of the sound that is played. Then, Chronos has a way to log the time in which sound was presented out of either the Right or Left channel. The difference between the OnsetTime and the sound presentation time will represent your Sound Onset Latency.

Image 3 Sound Onset Latency by Device and API

Chronos Audio Presentation Options
Chronos offers two options for presenting audio, MixMode1 and MixMode2. Both present great options for presenting audio but their use depend entirely on the study.

Image 4 Chronos audio setup

Mix Mode 1
Of the two sound output methods, Mix Mode 1 is used in the majority of cases. Mix Mode 1 presents audio with the least amount of Sound Onset latency with about 1ms of variability. Mix Mode 1 is meant to play sounds with a 1-2ms Sound Onset Delay. Mix Mode 1 can only handle one sound buffer at a time. The vast majority of users only need one sound buffer at a time anyway, which is why this playing method is the default and most popular method.

Image 5 Mix Mode1 Sound Onset Latency by delivery device and Operating System.

In Mix Mode 1, Chronos stores the sound that is about to play into its audio buffer so it is able to present it very quickly. As long as the sound does not change during playback (e.g. a new sound buffer is loaded in the middle of presentation), E-Prime is able to maintain this low latency.

Mix Mode 2
In a few rare cases, you may find that you need to present two audio buffers at the same time. In these instances, Mix Mode 2 will be ideal. Mix Mode 2 allows the user to select a Sound Onset Latency value. Chronos is then able to present sound within 1ms of the pre-defined latency value.

Chronos and Sound In
Just like its predecessor, the SRBox, Chronos comes equip with a voice key. Chronos’ voice key allows you to detect the onset time, offset time and duration of all vocal responses. Since Chronos is equip with an on-board sound card, it is also able to record the sound to which the voice key was responding.

Image 6 Chronos and included microphone

Chronos Audio Pass-Through
Chronos also offers a Pass-Through option for its audio presentation. This is primarily for users who would like to verify the quality and accuracy with which Chronos is recording audio. The Pass-Through allows you to hear the vocal response being made as they come in, making it an excellent troubleshooting tool.