Sound

• Vibrations propagated by waves of pressure through a material(s) (often air)

• The frequency of the wave determines the pitch of the sound we perceive

• The higher the frequency, the higher the pitch

• Frequency measured in Hz (vibrations per second)

• Humans can hear sounds within the range of 20Hz – 20,000Hz

• Human voice is 85Hz-255Hz

Audio with Arduino – Active Buzzer

• Produces a sound when supplied with electric current

• It is a digital output (on/off)

• You cannot use it to produce specific frequencies

• The leg marked with a + on top of the buzzer connects to the output pin

• The other leg connects to GND

Exercise 1

• Use your sketch from the homework to make the active buzzer beep and control the rate of beeping with the potentiometer

Audio with Arduino – Passive Buzzer

• Produces a square wave when supplied with a pulse of electric current

• The frequency of the tone is the frequency of the electric pulse

• Connections are the same as with the active buzzer

Audio with Arduino – Tone

• Use the tone function in a sketch

• Works with any digital pin (0-13)

• tone(pin,frequency)

• example: tone(8, 200);• this produces a 200Hz tone on a passive buzzer attached to pin 8

• Optional 3rd argument duration (in ms)• example: tone(8 , 200, 1000);• this produces a 200Hz tone on a passive buzzer attached to pin 8 for one second

• noTone(pin) – stops the tone

Try Melody example

Exercise 2

• Make a sketch that alters the pitch (frequency) of a tone based on an input of your choice

Amplification

• To get a louder sound, we need to apply greater voltage to the buzzer

• A transistor can be used to control a higher voltage source using a lower voltage source

• For example, we can use the 3.3V output pin to control a 5V supply to make our sound louder

• We will use the NPN (negative positive negative) transistor in your kit marked with “8050”

Amplification - Connections

• With the flat side of the transistor facing you

• NPN’s left leg -> GND

• NPN’s center leg -> Arduino output (tone)

• NPN’s right leg -> buzzer’s negative leg

• Buzzer’s positive leg -> 5V pin on Arduino

Volume control

• Add a potentiometer to the circuit to dial the volume up/down

• Connections:• Potentiometer’s center leg -> 5V

• Potentiometer’s outer leg (either) -> Buzzer’s positive leg

Map function

• Translates a number from one range to another range

• map(value, fromLow, fromHigh, toLow, toHigh)

• For example, if you want to use input from the potentiometer to set a tone frequency

• Potentiometer range: 0 – 1023

• Human hearing range: 20 – 20000

• int frequency = map(analogRead(A0), 0, 1023, 20, 20000);

• tone(8, frequency);

In Class MiniProject

• Work with assigned partner to make your own musical instrument• Sarah – Jared

• Anthony – Marissa

• Dan – Tori

• Tony – Andres

• Michael – Fred

• Ali – Francisco

• Giselle – Salvador

• Experiment and challenge yourself