Bootstrapping (statistics) In univariate problems, it is usually acceptable to resample the individual observations with replacement (case resampling below). In small samples, a parametric bootstrap approach might be preferred. For other problems, a smooth bootstrap will likely be preferred.
Below is a picture of a sound wave that has. been changed into alternating current by a microphone. and displayed on a CRO. If the sound is made louder and with a higher pitch, the shape of the wave changes as shown below. The amplitude has got bigger because the sound is louder. The frequency has increased. (there are more complete waves in the same time) because the sound has a higher pitch.
The speed of a sound wave in air depends on the temperature (c=331 + 0.6 T) where T is the temperature in o C. Often the change in the wave speed, and the resulting refraction, is due to a change in the local temperature of the air.