Category Chemistry

An orchestra has instruments that produce sounds in different ways, but all cause air to vibrate to carry the sound to listening ears. String instruments have vibrating strings that are bowed or plucked. Wind instruments cause a column of air to vibrate when the player blows into them. Instruments that create sounds by being struck or shaken are percussion instruments. Brass instruments resonate when air is blown into them.

Welcome to the world of classical music instruments! Musical instruments are grouped into different families based on the way the instrument makes its sound. There are four main families of instruments: strings, woodwinds, brass, and percussion. Here is how an orchestra is often set up:

The Strings

The four most commonly used instruments in the string family are the violin, the viola, the cello and the double (string) bass. They are all made by gluing pieces of wood together to form a hollow “sound box.” The quality of sound of one of these instruments depends on its shape, the wood it is made from, the thickness of both the top and back, and the varnish that coats its outside surface.

Four strings made of gut, synthetics, or steel are wrapped around pegs at one end of the instrument, tightly stretched across a “bridge,” and attached to a tailpiece at the other end. The pegs are used to tune the instrument (change the length of the string until it makes exactly the right sound). The strings are tuned in perfect “fifths” from each other – 5 notes apart.

The player makes the strings vibrate by plucking them, striking them, strumming them, or, most frequently, by drawing a bow across them. The bow is made of wood and horsehair. The instrument sounds different notes when the performer presses a finger down on the strings on the instrument’s neck, changing the length of the portion of the string that vibrates. The shorter the vibrating part of the string, the higher the sound produced.

The Woodwinds

Instruments in the woodwind family used to all be made of wood, hence the name, but now they can be made of wood, metal, plastic or some combination of materials. They are all tubes with an opening at one end and a mouthpiece at the other end. They each have rows of holes that are covered by metal caps called keys. Pressing on different keys produces different musical notes – the sound changes depending on where the air leaves the instrument (through one of the key holes or out the far end). There are three ways in which the woodwind family creates sound: by blowing air across the edge of or into the mouthpiece (flute or piccolo), by blowing air between a single reed and a fixed surface (clarinet and bass clarinet), or by blowing air between two reeds (oboe, English horn, bassoon, and contrabassoon).

The Brass

Brass instruments are essentially very long pipes that widen at their ends into a bell-like shape. The pipes have been curved and twisted into different shapes to make them easier to hold and play. Instruments in the brass family produce their sound when the player “buzzes” her or his lips while blowing air through the mouthpiece, kind of like making a “raspberry,” creating a vibrating column of air within the instrument. Most brass instruments have valves attached to their long pipes. When the player presses down on the valves, they open and close different parts of the pipe, increasing the length of the pipe when played and creating a lower sound. In addition to the valves, the player can select the pitch from a range of overtones or harmonics by changing his or her lip aperture and tension (known as the embouchure). The mouthpiece can also make a big difference in tone. Brass musicians can also insert mutes into the bell of their instrument to change the timbre of its sound.

The Percussion Family

The percussion section provides a variety of rhythms, textures and tone colors to orchestral music. Instruments in the percussion family make sound in one of three ways, by striking, shaking, or scraping. Percussion instruments can also be tuned or unturned. Tuned instruments play specific pitches or notes, just like the woodwind, brass and string instruments. Unturned instruments produce a sound with no definite pitch, like the sound of hitting two pieces of wood or metal together. Percussion instruments are an international family, representing musical styles from many different cultures. There are numerous kinds of percussion instruments, such as rattles, castanets, or tambourines. Keyboard instruments are a special class of percussion instrument.

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When we describe an object as hot, we are really comparing it with something else. The word does not mean anything by itself. We can say that we feel hot after exercise, that a cup of coffee is hot and that the surface of the Sun is hot, but we mean something quite different each time. An object can be hot compared with an ice cube but cold compared with boiling water. In fact, both the ice cube and the boiling water contain heat energy, but their temperatures are quite different. Temperature is a measure of how hot something is compared with an agreed scale. A small object with a temperature of 100°C may not have as much heat energy as a very large object with a temperature of 0°C.

I have often noted that when patients are running a fever with an infection, their face may be flushed and hot to the touch while their hands and feet may be cold and clammy. I think that the flushed face sensation causes one to feel hot when ill. And I think the cold hands and feet cause one to feel cold when ill. These can happen at the same time, and is truly miserable. Even though the body has a fever, the extremities (hands and feet) can be cool because of substances like adrenaline being pumped into circulation by the body in response to physiological insult (infection).

When running a fever, a person will often start getting dehydrated because of a lot of water loss (sweat, faster breathing). Adrenaline will increase a person’s blood pressure and heart rate. This is usually experienced as a flushed face. One of adrenaline’s functions is to constrict the blood vessels so as to raise the blood pressure. If the body is running dehydrated, this vessel constriction in the smaller vessels (the like in the hands and feet) may prevent good blood circulation in those parts of the body. Thus, the extremities can get feel cool to the touch because there is actually decreased blood flow there.

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Some aircraft can travel faster than the speed of sound. They travel ahead of the sounds they make. This produces a build-up of sound energy behind them that becomes a shock wave, heard as a sonic boom.

Have you ever seen a plane fly overhead at a supersonic speed? If so, you may have heard a loud “boom” as it passed by. Did it explode? Nope! You can still see it flying. Then what was that sound? It was a sonic boom.

A sonic boom is a loud sound kind of like an explosion. It’s caused by shock waves created by any object that travels through the air faster than the speed of sound. Sonic booms create huge amounts of sound energy.

When an object moves through the air, it makes pressure waves in front of and behind it. Have you ever seen a boat move through water? The bow waves (front) and stern waves (back) are similar to the invisible pressure waves created by an object as it moves through the air.

These pressure waves travel at the speed of sound. How fast is that? Pretty fast! Sound travels at different speeds through different types of materials. It also varies by altitude and temperature.

At sea level and 68° F, the speed of sound through air is about 761 miles per hour. At an altitude of about 20,000 feet where the atmosphere is thinner and colder, sound travels at about 660 miles per hour.

Austrian physicist Ernst Mach developed a method of measuring airspeed relative to the speed of sound. If a plane if flying at the speed of sound, it is said to be going Mach 1. A speed of Mach 2 would be twice the speed of sound.

As an object, such as an airplane, travels faster and faster, the pressure waves can’t get out of the way of each other. They build up and are compressed together. Eventually, they will form a single shock wave at the speed of sound.

The sonic boom we hear caused by an airplane flying at Mach 1 usually takes the form of a “double boom.” The first boom is caused by the change in air pressure as the nose of the plane reaches Mach 1, and the second boom is caused by the change in pressure that occurs when the tail of the plane passes and air pressure returns to normal.

As long as an airplane travels at Mach 1 or faster, it will generate a continuous sonic boom. All those in a narrow path below the airplane’s flight path will be able to hear the sonic boom as it passes overhead. This path is known as the “boom carpet.”

If you’re wondering about how pilots handle sonic booms, they actually don’t hear them. They can see the pressure waves around the plane, but people on board the airplane can’t hear the sonic boom. Like the wake of a ship, the boom carpet unrolls behind the airplane.

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Most sounds are not pure sounds of a single wavelength and frequency. Other frequencies are mixed in with the sound, creating the particular texture and tone of an individual voice or instrument. These frequencies are called harmonics.

When a musical instrument is playing a note, what we are actually hearing is the fundamental pitch, which is the pitch being played by the instrument, accompanied by a series of frequencies that are usually heard as a single composite tone. Those frequencies that are integer multiples of the fundamental pitch’s frequency are called harmonics. If a musician causes one of these harmonics to sound, without sounding its fundamental frequency, it is called playing a harmonic. This can be a little bit confusing, so let’s backtrack for a second. First off, we need to understand frequency.

Frequency is the rate at which a vibration occurs. This is measured in hertz (Hz), which is calculated by finding the number of vibrations per second. For example, a frequency that is vibrating 100 times per second would be described as having a frequency of 100Hz. When a pitch is produced, it creates a sound wave that vibrates at a specific frequency, the fundamental frequency, but it also causes a variety of other, higher frequencies to vibrate. These vibrations will be referred to as composite frequencies because they are a result of the vibrations of the fundamental frequency.

When the fundamental frequency and all of its composite frequencies are perceived by a listener, they are rarely heard as separate pitches. A listener will more likely perceive all of the frequencies wrapped together to form what we refer to as a composite tone. Any time an instrument produces a pitch, it will inherently produce a range of composite frequencies that add to the richness of the tone, and allow us to differentiate sound qualities, such as the difference between the way a violin sounds, and the way a guitar sounds. Ok, now that we’ve established a bit about how a pitch is heard, let’s make it even more complicated!

In order to discuss harmonics, we need to add one more component to the mix . . . MATH! Mathematics plays a big part in discussing harmonics, but lucky for us, none of it will get overly complex. For a composite frequency to be considered a harmonic, its frequency must be an integer multiple of the fundamental frequency. Don’t worries if that come on a little strong; we’re going to elaborate a bit on it now.

Let’s start with a hypothetical fundamental frequency of 100Hz. If we were to multiply it by any integer, our result would be considered an integer multiple of the fundamental frequency. In contrast, if we have a composite frequency, divide it by the fundamental frequency, and the result is an integer, then that composite frequency is an integer multiple. This is elaborated on a bit in the table.

Musical notation is a way of writing down musical sounds so that a singer or instrumentalist can reproduce them as the composer intends. As well as showing the pitch and length of the sounds, the notation gives information about how the notes should be played.

Musical notation, visual record of heard or imagined musical sound, or a set of visual instructions for performance of music. It usually takes written or printed form and is a conscious, comparatively laborious process. Its use is occasioned by one of two motives: as an aid to memory or as communication. By extension of the former, it helps the shaping of a composition to a level of sophistication that is impossible in a purely oral tradition. By extension of the latter, it serves as a means of preserving music (although incompletely and imperfectly) over long periods of time, facilitates performance by others, and presents music in a form suitable for study and analysis.

The primary elements of musical sound are pitch, or the location of musical sound on the scale (hence interval, or distance, between notes); duration (hence rhythm, metre, tempo); timbre or tone colour; and volume (hence stress, attack). In practice, no notation can handle all of these elements with precision. Most cope with a selection of them in varying degrees of refinement. Some handle only a single pattern—e.g., a melody, a rhythm; others handle several simultaneous patterns.

The position of staff notation as the first notational system to be described in this article acknowledges its international acceptance in the 20th century. As an indirect result of colonization, of missionary activity, and of ethno-musicological research—not because of any innate superiority—it has become a common language among many musical cultures.

Sounds travel as waves. It is the shape of the wave that determines the kind of sound that is produced. The pitch of a sound (whether it is high or low) depends on the frequency of the sound waves. The frequency is how many waves, or vibrations, the sound makes in one second. This is measured in hertz (Hz). One vibration per second is one hertz. How loud the sound is depends on the magnitude (or height) of its waves. The more energy the waves carry, the louder the sound. Loudness is measured in decibels (dB).

Sound energy travels in waves and is measured in frequency and amplitude. Amplitude measures how forceful the wave is. It is measured on a Logarithmic scale and reported in decibels or dBA of sound pressure. 0 dBA is the softest level that a person can hear. Normal speaking voices are around 65 dBA. A rock concert can reach about 120 dBA but is often at 100 dB.

Sounds that are 82 dBA or above can permanently damage your ears when exposed for a long period of time. The more sound pressure a sound has, the less time it takes to cause damage. For example, a sound at 85 dBA may take as long at 8 hours to cause permanent damage, while a sound at 97 dBA can start damaging hair cells after only 30 minutes of listening.

Frequency is measured in the number of sound vibrations in one second. A healthy ear can hear sounds of very low frequency, 20 Hertz (or 20 cycles per second), to a very high frequency of 20,000 Hertz. The lowest a key on the piano is 27 Hertz. The middle C key on a piano creates a 262 Hertz tone. The highest key on the piano is 4186 Hertz.

How loud a sound seems to depend on who’s listening. A young person playing rock up in their bedroom might not think their music is loud, but their parents in the room down below might have other ideas. In other words, how loud things seem is a subjective thing and not something we can easily measure. However, what makes one sound seem louder than another is the amount of energy that the source of the sound is pumping towards the listener in the form of pressure variations in the air. That’s the intensity of the sound.

Meters that measure sound levels work by calculating the pressure of the sound waves traveling through the air from a source of the noise. That’s why you’ll sometimes see them referred to as sound pressure level (SPL) meters. Devices like this give a measurement of sound intensity in units called decibels as we mentioned before. Telephone pioneer Alexander Graham Bell first devised this scale.