昨天的答案：

1. d   2. f   3. h   4. b   5. e   6. a   7. g   8. c

今天学习AUD和SON两个词根。

AUD, from the Latin verb audire, is the root that has to do with hearing. What is audible can be haerd. An audience is a group of listeners, sometimes seated in an auditorium. And audio today can mean almost anything that has to do with sound.

auditor. A person who formally examines and verifies financial accounts.

例句：It seems impossible that so many banks could have gotten into so much trouble if their auditors had been doing their jobs.

The auditing of a company's financial records by independent examiners on a regular basis is necessary to prevent "cooking the books," and thus to keep the company honest. We don't normally think of auditors as listening, since looking at and adding up numbers is their basic line of work, but auditors do have to listen to people's explanations, and perhaps that's the historical link. Hearing is more obviously part of another meaning of audit, the kind that college students do when they sit in on a class without taking exams or receiving an official grade. 

auditory. (1) Perceived or experienced through hearing. (2) Of or relating to the sense or organs of hearing.

例句：With the "surround-sound" systems in most theaters, going to a movie is now an auditory experience as much as a visual one.

Auditory is close in meaning to acoustic and acoustical, but auditory usually refers more to hearing than to sound. For instance, many dogs have great auditory (not acoustic) powers, and the auditory nerve(神经) lets us hear by connecting the inner ear to the brain. Acoustic and acoustical instead refer especially to instruments and the conditions under which sound can be heard; so architects concern themselves with the acoustic properties of an auditorium, and instrument makers with those of a clarinet or piano.

audition. A trial performance to evaluate a performer's skills.

例句：Auditions for Broadway shows attract so many hopeful unknown performers that everyone in the business calls them "cattle calls."

Most stars are discovered at auditions, where a number of candidates read the same part and the director chooses. Lana Turner famously skipped the audition process and was instead discovered by an agent sipping a soda in a Sunset Boulevard cafe at age 16. Audition can also be a verb; so, for example, after Miss Turner gained her stardom, actors had to audition to be her leading man. But when musicians audition for a job in an orchestra, it's usually behind a screen so that the judges won't even know their sex and therefore can't do anything but listen.

inaudible. Not heard or capable of being heard.

例句：The coach spoke to her in a low voice that was inaudible to the rest of the gymnastics team.

With its negative prefix in-, inaudible means the opposite of audible. What's clearly audible to you may be inaudible to your elderly grandfather. Modern spy technology can turn inaudible conversations into audible ones with the use of high-powered directional microphones, so if you think you're being spied on, make sure there's a lot of other noise around you. And if you don't want everyone around you to know you're bored, keep your sighs inaudible.

SON(这里指声音，不是儿子) is the Latin root meaning "sound." Sonata, meaning a piece for one or two instruments, was originally an Italian verb meaning "sounded" (when singers were involved, the Italians used a different verb). And sonorous means full, loud, or rich in sound.

sonic. (1) Having to do with sound. (2) Having to do with the speed of sound in air (about 750 miles per hour).

例句：A sonic depth finder can easily determine the depth of a lake by bouncing a sound signal off the bottom.

A sonic boom is an explosive sound created by a shock wave formed at the nose of an aircraft. In 1947 a plane piloted by Chuck Yeager burst the "sound barrier" and created the first sonic boom. In the decades afterward sonic booms became the first sonic boom. In the decades afterward sonic booms became a familiar sound to Americans. (Because of steps that were eventually taken, sonic booms are rarely heard anymore.) Today sonic is often used by ambitious rock musicians to describe their experimental sounds.

dissonant. (1) Clashing or discordant, especially in music. (2) Incompatible or disagreeing.

例句：Critics of the health-care plan pointed to its two seemingly dissonant goals: cost containment, which would try to control spending, and universal coverage, which could increase spending.

Since dissonant includes the negative prefix dis-, what is dissonant sounds or feels unresolved, unharmonic, and clashing. Early in the 20th, composers such as Arnold Schoenberg and his students developed the use of dissonance in music as a style in itself. But to many listeners, the sounds in such music are still unbearable, and most continue to prefer music based on traditional tonality. Dissonant is now often used without referring to sound at all. Cognitive dissonance, for example, is what happens when you believe two different things that can't actually both be true.

resonance. (1) A continuing or echoing of sound. (2) A richness and variety in the depth and quality of sound.

例句：The resonance of James Earl Jones's vocal tones in such roles as Darth Vader made his voice one of the most recognizable of its time.

Many of the finest musical instruments possess a high degree of resonance which, by producing additional vibrations and echoes of the original sound, enriches and amplifies it. Violins made by the Italian masters Stradivari and Guarneri possess a quality of resonance that later violinmakers have never precisely duplicated. And you may have noticed how a particular note will start something in a room buzzing, as one of the touching surfaces begins to resonate with the note. Because of that, resonance and resonate--along with the adjective resonant--aren't always used to describe sound. For example, you may say that a novel resonates strongly with you because the author seems to be describing your own experiences and feelings.

ultrasonic. Having a frequency higher than what can be heard by the human ear.

例句：My grandfather's dog is always pricking up its ears at some ultrasonic signal, while he himself is so deaf he can't even hear a big singing.

Ultrasound, or ultrasonography, works on the principle that sound is reflected at different speeds by tissues or substances of different densities. Ultrasound technology has been used medically since the 1940s. Sonograms, the pictures produced by ultrasound, can reveal heart defects, tumors, and gallstones; since low-power ultrasonic waves don't present any risks to a body, they're most often used to display fetuses during pregnancy in order to make sure they're healthy. Ultrasonics has many other uses, including underwater sonar sensing. High-power ultrasonics are so intense that they're actually used for drilling and welding.

Quiz:

Indicate whether the following pairs of words have the same or different meanings:

1. dissonant / jarring

2. inaudible / invisible

3. resonance / richness

4. audition / tryout

5. ultrasonic / radical

6. auditor / performer

7. sonic / loud 

8. auditory / hearing-related