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Stage 3: Give It a Voice

Course progressStage 3 of 10
~45 min
Your robot workspace

We code the mBot in mBlock 5. Keep this tab open all week. Open in a new tab — don’t use the buttons in this page to leave the course.

Code your robotmBlock 5Open in a new tab ↗USB / Bluetooth setupConnect your mBotOpen in a new tab ↗
Build

a start-up beep and a short tune your mBot plays on command

Learn

how a note is a pitch and a length, and how to make a melody from a sequence

Ship

an mBot that beeps to tell you what it is doing

Teacher demo

Before campers code, show the room:

  1. Play one note. Then play a higher note. Say: "A higher number is a higher sound."
  2. Play three notes in a row to make a tiny tune.
  3. Pair sound with light: beep and flash green at the same moment. Point out that a robot can use sound and light together to get your attention.

The big idea​

Your mBot has a buzzer — a small speaker that plays one sound at a time. Each sound is a note. A note has two parts: a pitch (how high or low it sounds) and a length (how long it lasts). Play notes one after another, and you have a melody.

Sound is the robot's loudest way to talk to you. A beep can mean "I'm starting," "I'm done," or "I see something." You will use beeps as signals all week — they tell you what the robot is thinking even when you are not looking at it.

   low note  ───  high note
    C4   D4   E4   F4   G4   ...   (numbers go up = pitch goes up)
The buzzer
The mBot buzzer playing musical notes

One buzzer, one note at a time. A melody is just notes in a sequence.

New words
buzzer
the small speaker that plays sounds
note
one sound, with a pitch and a length
pitch
how high or low a sound is
beat
how long a note lasts
melody
notes played one after another
Before you start

Make sure you've finished Stage 2: Light It Up. Your robot drives, glows, and is Connected.

Build it​

Step 1 — One beep​

The simplest sound: a single note.

Beep once

when green flag clicked
play tone on note (C5) for (0.5) beats :: sound

Click the flag. One short beep.

Step 2 — Three notes make a tune​

Stack notes in a sequence. Try going up the scale.

Climbing tune

when green flag clicked
play tone on note (C5) for (0.5) beats :: sound
play tone on note (E5) for (0.5) beats :: sound
play tone on note (G5) for (0.5) beats :: sound

Run it. Three notes, climbing higher. You just wrote a melody.

Step 3 — A start-up signal​

Combine sound and light into a "robot is awake" signal — the kind real robots play when they turn on.

Power-on signal

when green flag clicked
set led [all v] to color [#57fff4] :: looks
play tone on note (G5) for (0.25) beats :: sound
play tone on note (C6) for (0.5) beats :: sound
set led [all v] to color [#000000] :: looks

Run it. The robot flashes cyan and chirps two quick notes, then the light goes dark. That is your robot saying "I'm ready."

Pacing Lab​

This lab is required before you move on. The goal is a signal another person can recognize, not random noise.

Part A — Compose a four-note tune (15 minutes)​

On paper, plan four notes before you build them:

Note 1: ____  length ____
Note 2: ____  length ____
Note 3: ____  length ____
Note 4: ____  length ____

Build it, listen, and adjust. Changing one note's length changes the whole feel — try making the last note longer.

Part B — Name that signal (10 minutes)​

Play your power-on signal for a partner alongside a different beep (like a "done" beep). Can they tell the two apart? A good signal is one you can recognize without looking.

Understand it​

A melody is a sequence, the same idea you used to drive in Stage 1 — blocks running in order, one after another. The only new thing is that each block makes a sound instead of a movement. That is worth noticing: once you learn sequence, you can use it for motors, lights, or sound. One idea, many uses.

The buzzer plays only one note at a time, so timing matters. A note's length is also a tiny wait — the program pauses on that line until the note finishes. That is why you do not need separate wait blocks between notes the way you did between LED colors.

Try this​

Learning beat

Try this

Three short experiments. Predict before you run, then test your guess.

Predict first

If you change every note's length from 0.5 to 1, will the tune sound higher, lower, or just slower? Decide first, then test.

Compare

Play your tune going up the scale, then copy it and reverse the order so it goes down. Which one sounds happy, which sounds like an ending?

Connect

You can now signal with sound. In Stage 5, the robot will beep when it sees a wall. What beep would you use for "danger"? A high fast one, or a low slow one?

Test your stage​

  • Your robot plays a single beep on the green flag.
  • Your robot plays at least three notes in a row as a melody.
  • Your power-on signal pairs a sound with a light.
  • Design check. Play your "ready" signal and your tune back to back. Do they sound different enough to tell apart?

If it breaks​

  • No sound at all. Check that mBlock says Connected and the volume of the buzzer is not set to 0. Make sure you used a note block, not a wait block.
  • The notes blur together. Some notes are very short. Give each note a length of at least 0.25 beats so you can hear it.
  • It plays once and won't replay. That is normal — click the green flag again to replay. If you want it to loop, wrap the notes in a repeat block.
Coach notes

This is the loudest stage of the week — twenty buzzers at once is a lot. Consider giving each table a turn to test, or set a "compose silently, test on my signal" rhythm so you can actually hear individual robots.

The musical kids will run far ahead here; point them at the hard stretch and the song challenge. The kids who find pitch confusing do fine with "bigger number = higher sound" — they do not need to know note names.

Tie every signal back to meaning. The point is not music for its own sake; it is that sound is a channel the robot uses to tell the human what is happening. That framing carries into the sensor stages.