Eggs that you buy from the store will not stay fresh for long  without refrigeration. Eggs that come right from the chicken can  kept at room temperature for weeks. Store bo â¦ ught eggs should be  refrigerated within a few hours of buying them just to be safe.ven with its natural (but easily cracked) calcium-carbonate container, a hard-cooked egg is a perishabl â¦ e food, so it shouldn't be kept at room temperature for more than two hours.   If kept in an unbroken shell and in the refrigerator about a week.
The human range is commonly given as 20 to 20,000 Hz, though there is considerable variation between individuals, especially at high frequencies, and a gradual loss of sensitivity to higher frequencies with age is considered normal. Sensitivity also varies with frequency, as shown by equal-loudness contours.
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.