Working donkeys are often associated with those living at or below subsistence levels. Small numbers of donkeys are kept for breeding or as pets in developed countries. A male donkey or ass is called a jack, a female a jenny or jennet; a young donkey is a foal.Jack donkeys are often used to mate with female horses to produce mules.he donkey has been used as a working animal for at least 5000 years. Of the more than 40 million donkeys in the world, about 96% are in underdeveloped countries, where they are used principally as pack animals or for draught work in transport or agriculture.
In simplistic language, every matter in this world vibrates, so that vibration we call frequency, and we measure it in Hz. The sound has its own frequency which is also measurable in Hz. The guy in the beginning of the video says that everything owes its existence to sound.
Small mammals like Dogs, Cats etc. responds to 22-25 kHz US and Rats to 60-72 kHz. Insects like Mosquitoes, Flies responds to 38-44 kHz. What is Ultrasound? The hearing property of human ear is limited. Human ear can perceive sound with in a frequency range of 20 Hz to 20 kHz. The sound frequency below 20 Hz is Infrasonic sound and above 20 kHz is Ultrasonic sound. Human ear is not sensitive to US because the eardrum cannot vibrate as fast as US. Ultrasound has high frequency, so the wave is very powerful.