Audio hardware

Infant testing procedures typically either have sound from front and center (as in PLP), or from the two sides of the room (as in HPP). Sound in HPP is usually played either in stereo from both speakers simultaneously (as in Saffran et al., 1996), or is played only from the same side of the room as the attention-getter. Dichotic presentation is relatively rare, but there are situations in which it would be advantageous to be able to play different sounds from multiple locations at once, such as in studies exploring infant perception of speech in the presence of background noise or studies of speech perception in deaf children with CIs, where little is known about their use of binaural cues.

BITTSy software allows the researcher to output sound individually over any of the speakers available to their system, as well as output sound in stereo (simultaneous presentation of a single file through the left and right channels).

In a standard stereo audio (2.1) system, there is a left channel and a right channel, allowing for up to two speakers. With a surround sound capable system (5.1 or 7.1), you can control more speakers individually (5 or 7 locations, respectively).

Any speakers that are compatible with your computer will work for BITTSy.

• Ensure that your selected speakers will play audio with satisfactory quality and volume for your studies (or additionally purchase an amplifier for the latter).

• Ensure that you have purchased the correct cables to connect the audio output jacks on your computer to your speaker input jacks.

We recommend using wired connections to speakers, rather than connecting through Bluetooth.

Why not use internal speakers on television displays?

This section is just for those curious about why we recommend a separate speaker system.

Some labs (including ours) may select audio-capable TVs as their displays for use with BITTSy. There are a number of reasons to prefer separate speakers over internal speakers on TVs when running BITTSy studies. Here are the main reasons why we recommend this:

• BITTSy has not been tested with presenting audio over an HDMI audio signal (the main reason - which stems from several of these others!)

• Computers with HDMI outputs have separate sound drivers listed for HDMI and for devices plugged into audio-only ports, which may have different default settings that could complicate setting up or standardizing how audio is presented to different locations in BITTSy.

• Graphics cards with multiple HDMI output ports are more expensive than cards with more non-audio-carrying port types such as VGA and DisplayPort - and computers that can be equipped with these cards are correspondingly more expensive.

• Modern TVs often accept only HDMI input, do not have an option of supplying audio from an audio jack on the computer instead, and output two-channel audio from the left and right side of the device. For left-side and right-side screens that you wish to associate with only left- or right-channel audio (i.e. for HPP studies), this combination makes it impossible to separate channels and present them from the appropriate side. (E.g., a command from BITTSy to play audio on the left would be carried over HDMI to both TV speakers, and both would play audio on the left-hand side of the device - rather than the intended effect of audio being played from only the device that is on the left side of the room.)

• Internal speakers on TVs are generally of poorer quality, and present audio signals with less fidelity, than what can be obtained with external speakers.