对于机场飞机噪声应以( )作为噪声源评价量。
A．倍频带声压级
B．声功率级
C．等效连续A声级
D．计权等效连续感觉噪声级
参考答案：D
解析： 计权有效连续感觉噪声级，用于评价航空噪声，其特点在于既考虑了在24h的时间内，飞机通过某一固定点所产生的总噪声级，同时也考虑了不同时间内飞机对周围环境所造成的影响。我国现行《机场周围区域环境飞机噪声标准》即规定采用此法进行评价。
| Mankind’s fascination with gold is as old as civilization itself. The ancient Egyptians esteemed gold, which had religious significance to them, and King Tutankhamen was buried in a solid-gold coffin 3300 years ago. People have always longed to possess gold. Unfortunately, this longing has also brought out the worst in the human character. The Spanish conquistadores robbed palaces, temples and graves, and killed thousands of Indians in their ruthless search for gold. Often the only rule in young California during the days of the gold rush was exercised by the mob with a rope. Even today, the economic running of South Africa’s gold mines depends largely on the employment of black labourens who are paid about 40 a month, plus room and board, and who must work in conditions that can only be described as cruel. About 400 miners are killed in mine accidents in South Africa each year, or one for every two tons of gold produced. Much of gold’s value lies in its scarcity. Only about 80,000 tons have been mined in the history of the world. All of it could be stored in a vault 60 feet square, or a supertanker. Great Britain was the first country to adopt the gold standard, when the Master of Mint, Sir Isaac Newton, established a fixed price for gold in 1717. But until the big discoveries of gold in the last half of the nineteenth century — starting in California in 1848 and later in Australia and South Africa — there simply wasn’t enough gold around for all the trading nations to link their currencies to the precious metal. An out-of-work prospector named George Harrison launched South Africa into the gold age in 1886 when he discovered the metal on a farm near what is now Johannesburg. Harrison was given a 12 reward by the farmer. He then disappeared and reportedly was eaten by a lion. Historically, the desire to hoard gold at home has been primarily an occupation of the working and peasant classes, who have no faith in paper money. George Bernard Shaw defended their instincts eloquently: "You have to choose between trusting to the natural stability of gold and the natural stability of the honesty and intelligence of the members of the government", he said, "and with due respect to these gentlemen, I advise you to vote for gold." |
One of the problems with gold is that ______ .
A．( it loses its shape too easily
B．( it changes the human characters
C．( it entails danger to miners
D．( it costs money to produce
