Tag Archives: Audio

Configuring a Classroom for Distance Learning (on a budget!)

A small private school that serves male students from at-risk neighborhoods asked me to teach a course remotely to their 10th grade students.  One of the first challenges we faced was configuring the classroom for distance learning to provide an appropriate environment for conducting the daily lessons.  The school has Internet access and a campus-wide wireless network. Several of the classrooms have SMART MX086 interactive display boards from SMART Technologies.  Additionally, each student has a Chromebook with camera, microphone, and speakers.

A Problem with Feedback

During an initial site visit, we started a test session with Zoom.  I hosted the meeting and took my laptop into one classroom. The Head of School remained with his connected via HDMI to a SMART board in another.  We immediately discovered there was going to be a problem with audio feedback. The mics in the Chromebooks amplify the sound from the board’s built-in speakers and produce a screeching hiss.  I concluded my visit with an action item to design a solution that would reduce or eliminate this feedback.

After doing some research, I discovered that cardioid microphones are designed for this scenario.  A cardioid microphone picks up sound to the side and in front of the microphone, but not from behind it.  They are so named because the mic’s sensitive area roughly resembles a heart when drawn in cross-section.  I purchased two of these cardioid microphones with long cables and stands. I also bought a small audio mixer and a cable to connect its output to the SMART board’s audio in port.  We planned to position the microphones on either side of the room, facing away from the SMART board. Running them through the mixer would provide a single, merged audio signal to the SMART board.

Testing the Planned Solution

I returned to the school a day before the course was to start. We wanted to set up and test the audio configuration.  Sadly, it did not work.  With a laptop connected to one of the SMART board’s HDMI input ports, we could not get any sound from the mixer.  Further, we could not route the signal from the mixer directly to the laptop because the laptop had only a combined microphone/headphones jack.  This jack needs a cable with a special tip that carries the left and right output signals to the headphones as well as the audio input signal from the microphone.  Even if we had had an appropriate cable, this port expects an input signal with much less voltage than the mixer was supplying.  (The mixer needs to go into a line in port rather than a microphone port.)

We discovered that the SMART board runs an Android operating system and had a Zoom client available for it.  We believed, therefore, that we could eliminate the laptop. With the native Zoom client, we thought we could use the mixer (connected to the board’s audio in port) as the microphone.  This also did not work.  We ultimately learned that the SMART board’s audio in port is active ONLY when the board is connected to a laptop’s display using the VGA port.  Unlike HDMI, VGA does not carry an audio signal. To get sound from the laptop when driving the board’s display via VGA, one must connect the laptop’s audio out/headphones port to the board’s audio in port.  When connected this way, it seems that the audio signal from the laptop is routed directly to the board’s speakers.


I realized that what we probably needed was a USB external sound card with a line in port.  The would allow us to route the mixer’s output into the laptop. I found two that looked promising: the Startech 7.1 USB Sound Card and the Envel Headset Adapter (which isn’t really a sound card; instead, it is an adapter that detects what is plugged into it and adjusts accordingly).  Because they were relatively inexpensive (less than $40 combined), I ordered both.

When these new components arrived later that week, we were pleased to see that both worked!  Now back to using the laptop connected to the SMART board via HMDI, we can use either sound device. We plug the output cable from the mixer into the device and select the appropriate audio input sound source in the Zoom client. Each student also joins the meeting on his own Chromebook, but with the volume down and the microphone muted.  We positioned the two microphone stands near the front of the classroom, one on each side. They are almost even with the first row of desks, facing away from the SMART board.

Analyzing the Results

After configuring this classroom for distance learning, the sound quality is pretty good.  Students hear me through the SMART board’s speakers. There is virtually no feedback as long as they leave their microphones off. I can hear the class through the two microphones whose signals are being fed through the mixer into the laptop. The set up works well when calling on an individual students. It is difficult to hear who is speaking in more open class discussions, though.

To help compensate, class discussions are now a blend of lecture and challenge/response. I go around the seating chart and ask specific students to contribute.  In truth, this may actually help them stay engaged. After all, they do not know when I might ask them to answer a question. If I need to meet individually with a student, I first mute the main session. Then, I assign the student to a Zoom breakout room.  The student unmutes his microphone, turns up the volume on his Chromebook, and we can converse one-on-one.

Impact on the Bottom Line

Not including the equipment the school already owned, configuring this classroom for distance learning cost under $170. It would have worked without the Startech sound card thus bringing the cost to around $140.  Specifically, we purchased the following:

Ohuhu triple boom microphone stand (2-pack)$40
Amazon Basics dynamic vocal cardioid microphone w/cable2@$21
Donner DEL-8i2 4-channel stereo audio mixer$34
MillSO 6.35mm (1/4″) male to 3.5mm (1/8″) male audio cable$13
Startech 7.1 USB sound card$31
Envel USB headset adapter$9
Table 1: Approximate costs for equipment purchased to configure classroom for distance learning

Note: Neither I nor the Excalibur Solutions STEM Academy™ nor Excalibur Solutions is affiliated in any way with the companies that manufacture the products mentioned in this article, nor have any of the aforementioned parties been compensated for discussing their use. These products were purchased and are being used in the manner described in the article. No warranty, either expressed or implied, is made as to the suitability of these products for use in any context.