Audio settings and channel crossover

BITTSy can send an audio file to play over just one speaker out of the available array for your system. How it actually does this is to send file information to the desired speaker to play at full volume, and silence of the same length to play at the other speakers. (The silence does not block those speakers from playing another audio file from a subsequent protocol line; the two will be played simultaneously, and since one has no audio information and is completely silent, it does not affect the second file's playback.)

It is possible to experience an effect where audio that is sent to only one speaker is also heard at a lower volume on another speaker - an audio channel crossover effect. This is not caused by BITTSy, but could be a result of 1) a cable/audio jack issue, 2) a sound card driver "audio enhancement" effect, or 3) an issue with your sound card.

If you get a warning about Waves MaxxAudio whenever you open BITTSy, #2 should be fixed first. Skip to the sound card driver section below.

Before you start, make sure the audio file you're using is in one of our suggested file formats. When playing file formats such as .aiff (native to Mac computers rather than Windows), some users find that they can play the file, but it does not play correctly with respect to channel separation, and converting to a .wav format resolves the issue. See this page for more info.

Audio cables and jacks

The first possibility is the easiest to check. Unplug the cable that runs from the 3.5mm audio jack on your computer to your speakers and plug in a pair of headphones (which you know work!) instead. Wired earbuds work especially well because you can put in just one at a time to check that the channel that is not supposed to be playing audio is in fact silent.

It's best to try headphones that match the jack type on the computer, either stereo audio (3 metal sections separated by 2 rings) or stereo audio plus microphone input (four sections separated by 3 rings). If your computer has a separate dedicated microphone jack nearby, the audio output jack will be just stereo audio.

Test your audio with these headphones. You can do this easily with a test audio file that you know to be only in one channel with silence in the other, or where the two channels are completely different, and playing it in Windows Media Player (BITTSy relies on the same codecs and calls as Windows Media Player and playback should be the same between the two), but you could also run a simple BITTSy protocol that plays a file to just one side, waits for a keypress, then plays to the other.

If the headphones play audio as intended: You may need to replace the audio cable that runs to your speakers. It may have been damaged, or the sections on its cable may be misaligned with respect to your computer's audio jack. You can test the latter possibility in the same manner described below for headphones. These cables are cheap, so it is worth buying a couple more from different manufacturers and returning whatever doesn't work. If nothing seems to align with your computer, there may have been a manufacturing issue; check if it is under warranty and proceed from there.

If the headphones have the same crossover issue: It's less likely that the issue is with the speaker audio cable itself, but there could be a problem with the audio jack on your computer. Different manufacturers can place the sections and buffer rings (as you see on the diagram above) in slightly different places, and a misalignment between cable and jack can mean that information the computer is sending to one channel can be also received on the very edge of another. This will cause a very faint and often static-sounding version of the audio to be played on the other channel, while a fuller-sounding version plays to the correct one. Try unplugging your headphones slowly and very slightly as you listen, and see if the crossover issue resolves at any point. If this is your issue, there will be a place where you can leave it and both left-only and right-only audio will play cleanly, without crossover and at full volume.

If it doesn't seem to be a jack alignment issue: Check your sound card driver next (below).

Sound card drivers (and the evils of Waves MaxxAudio)

Sound card drivers take audio information (such as audio files that BITTSy opens) and format that information into the final signal that is sent via your audio jack and cable to play through your speakers. Any functional sound driver will correctly take in all the specifics of the audio file, and take information from the software that requested the file about how to play it - but importantly, sound drivers can use their own settings within the formatting step to change the final output from being played exactly how the file and requesting program specified.

These are audio "enhancements" and may include rebalancing across frequency ranges (such as a bass boost), balancing perceived loudness across files (rather than playing them with their encoded average intensities), and introducing slight audio channel crossover for a more "natural" sound. These can be nice for listening to music, but for experiments, it is extremely important that stimuli are played with fidelity, exactly as they were designed. And since these audio enhancements are applied at the end, right before the signal is sent to the speakers, BITTSy can't do anything about it - its request to play the file to only one channel, with complete silence on the other, is overridden and remixed to have crossover.

First, ensure that audio enhancements are turned off within Windows 10. See instructions here.

Now that those are disabled, you may still have more places where these kinds of enhancements are turned on, or you may have a sound driver that doesn't have options to turn them off. Check what sound driver(s) is/are active on your computer by opening Device Manager (type it in your search bar) and expanding the "Sound, video and game controllers" menu. There may be several listed, from companies such as Intel and Realtek.

Search for each of these on your computer and see if you have a program installed along with that driver that serves as a control panel for it. In this program, look for where to turn off audio enhancements (search online for support for your specific driver if you need to.)

Waves MaxxAudio is a type of Realtek driver that ships with some Dell computers, and applies a lot of audio "enhancements" but (at present) has no options to turn them off. If you have Waves MaxxAudio on your computer, your only recourse is to uninstall it and revert to a generic Windows sound driver. Because Waves MaxxAudio causes so many problems, BITTSy versions 1.32 and later will specifically check to see if Waves MaxxAudio is installed and display a warning if it detects it on your system, every time you open BITTSy.

The warning dialog contains a link with steps to fix the issue and install the generic sound driver. Once you restart your computer, check that Waves MaxxAudio is really gone (open BITTSy and it will check for you!) Your computer will scan for new drivers on restart, and may find an older version of Waves MaxxAudio that wasn't removed during the uninstall, or could download a new copy of Waves MaxxAudio via Windows Update whenever an updated driver is made available. If this happens, you'll need to repeat the process again until it is completely gone.

Under the Advanced Settings menu in BITTSy, there are also options to pause or disable Waves MaxxAudio. These can be used if you are unable to uninstall it. However, you will need to re-select to disable Waves whenever you download and start using a new version of BITTSy.

It is possible that there are other sound drivers out there that are just as bad as Waves MaxxAudio... this is just the one that several of our beta testing labs encountered. If you have a different driver but are having similar audio problems, you can still use our instructions to disable it and replace it with a generic driver. (If that fixes the issue, let us know what your driver was so we can add it to the bad list!)

Sound card manufacturing issue

A final possibility is that there could be a defect in your sound card that is causing it to have electrical crossover between audio channels. This is rare, because the manufacturing standards for channel crossover at normal playing volumes are set well below human hearing thresholds - there would need to be a major issue to make them even barely audible. But if you've eliminated other possibilities, it may be best to try to replace your sound card. Check warranties, whether your sound card is the standard one for your computer model, and what other sound cards are compatible.

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