NumberSpeaker is an Arduino library for reading numbers using a speaker. A human voice from WAV files is encoded into bytes which are stored in program memory and played back using PWM to drive a speaker. The audio waveforms are stored in memory and occupy about half of the Arduino's program space.

Example (Video): https://swharden.com/static/2023/08/19/numbers.webm

• Connect a speaker to pin 11
• Open the Arduino IDE and create a new sketch
• Press CTRL+SHIFT+i to open the library manager
• Search for NumberSpeaker and select Install
• Paste the following into your sketch

#include <NumberSpeaker.h>

NumberSpeaker numberSpeaker = NumberSpeaker();

void setup() {
  numberSpeaker.begin(); // connect a speaker to pin 11
}

void loop() {

  numberSpeaker.speak_int(1234567);
  delay(500);

  numberSpeaker.speak_float(123.4567);
  delay(500);

  numberSpeaker.speak_string("69.420.42");
  delay(500);

  numberSpeaker.speak_char('6');
  numberSpeaker.speak_char('.');
  numberSpeaker.speak_char('9');
  delay(500);

  for (;;) {}
}

• Speaking Numbers with a Microcontroller - A blog post describing the strategy used to encode audio files, store them in program memory, and play them back using a speaker.

• Play Audio from SPI Flash with a Microcontroller - A blog post describing how to use a microcontroller to drive a speaker using PWM from audio levels stored in a SPI flash chip. This strategy is useful for users who wish to play longer audio clips or use less program memory.

• Talkie is an official Arduino speech synthesis library. It is a software implementation of the Texas Instruments speech synthesis architecture from the late 1970s. I found the voice to be poor quality for reading numbers, but it may be useful to users seeking more complex phrases or who are concerned about demands on program memory.