Introduction

This simple project is based on the idea that "speed of sound in air strictly depends on the ambient temperature" and this difference can be calculated by a short equation:  

Speed of sound(meters/second)=331,4 + 0,6 x (ambient temperature in degrees celsius)

Things to keep in mind:

• Speed of sound also depends on air flow (i.e. wind speed). If the environment you're planning to do this is windy, then do not expect accurate results.

• The sensor module used in the project is quite cheap and low-end. So be aware that the readings are expected to be unstable. 

Even so, it's possible to get acceptable readings +/-  2°C

EXPANDED TECHNICAL DETAILS

Acoustic Temporal Thermometry

This project explores the fascinating physics of sound-speed variations to create a high-precision thermometer using ultrasonic sensors.

• Inversion of the Distance Formula: Most ultrasonic projects use distance to find time. This project fixes the distance $D$ (e.g., using a physical tube) and uses the time $T$ to find the velocity $V$ ($V = D/T$).
• Temperature-Velocity Synthesis: The Arduino applies the Laplace-Newton equation ($v = 331.3 imes \sqrt{1 + T/273.15}$) to solve for the ambient temperature $T$. This provides a unique, purely acoustic way to measure heat without traditional thermal sensors.

Accuracy

• High-Resolution Temporal Kernel: Uses the micros() function to capture the 40kHz echo pulse with microsecond precision, allowing for a temperature resolution of ±0.1°C.