5 to 6 months. Practices intonation by making her voice rise and fall, often in response to baby talk and your facial expressions. Red flag: If your child isn't making vocal sounds by the time she's 6 months old, talk with her doctor. 7 to 12 months. Babbles with greater diversity, making new sound combinations and intonations. Red flag: If your child isn't making vocal sounds by age 7 months, talk with his doctor.
Relative humidity is a measure of the amount of moisture in the air relative to the total amount of moisture the air can hold. For instance, if the relative humidity was 50%, then the air is only half saturated with moisture. Warmer air can hold more moisture than colder air. Why is relative humidity important?
This is because a higher-than-normal temperature (a warm, balmy day) tends to be accompanied by a higher-than-normal barometric pressure of the atmosphere. That is, high temperature tends to decrease air density, while high pressure tends to increase air density. The air density ratio column in Table 3.1-1, which is the ratio of standard air density at altitude to the standard air density at sea level, shows that the air density decreases rapidly as altitude increases.