I did a lab in class and the data I got might be a bit skewed (this is homework). When I graphed the speed of sound (m/s; y-axis) vs. air temp (degrees Celsius; x-axis), my graph resembled that of the graph of $y=x^3$ where it goes from concave down to concave up. Does my data contain errors or is this actually the way the graph was supposed to turn out?
Experiment: We took a Pasco Resonance tube and heated it up with a hair dryer to about 38 degrees Celsius. Then we placed a microphone near the open end (other side was closed) and used a dog clicker to make a sound right next to the microphone. The microphone recorded the sound as it went into the tube, bounced back, and came back to the microphone. The room was a standard college Physics classroom (room temp, regular pressure, humidity, etc...)