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Physics and Music

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Sevanthi R

on 16 January 2013

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Transcript of Physics and Music

Physics in Music by: Sevanthi, Holiana, Abijah What are Waves? Sound Waves String Instruments Wind Instruments Vocal Cords Concert Open Pipe Instruments Waves are the transfer of energy through a medium without the transfer of matter. Depending on the types of waves being produced, the waves will either have crests and troughs (transverse) or refractions and compressions (longitudinal).
An example of transverse waves would be light waves, in which the energy do not need a medium to travel through.
Longitudinal waves cannot travel through a vacuum, so they may only travel through a solid, liquid or gas (air being a common medium). In a series of waves, one crest and trough or one compression and refraction is one wave or cycle. The number of complete waves or cycles in one second is known as the frequency of the wave. Other aspects of waves are the amplitude, in which it is the maximum displacement from the equilibrium position; and wavelength, in which it is the length measured of one wave in the medium (measured in cm or m).
Next, when two or more pulses of a wave are present in a medium, interference occurs. String instruments are either strummed, plucked or bowed, resulting in different sounds.

When an instrument is plucked or strummed, the input of energy is very low, so maintaining that rich note is very short, also making any higher harmonics to fade away faster which leaves only the fundamental frequency and other weaker harmonics.

Using a bow (bowed instruments) allows a constant and continuous flow of energy into the instrument, which maintains that rich, harmonic sound. Sound is a mechanical wave that results from the back and forth vibration of particles in a medium.
Sound waves are interpreted as a form of energy that stimulates the sense of hearing in animal species (including humans).
Sounds are produce by sources of vibration, and these sources create longitudinal waves that are transmitted through a medium (e.g. air) before reaching our ears. The Sound Spectrum The spectrum is broken down into three categories; Infrasonic sounds, Audible sounds and Ultrasonic sounds. Infrasonic sounds have frequencies of less than 20 Hz. Since the frequency is too low, humans are not able to hear these sounds; instead they can feel them as a rumble that passes through their body (e.g. a light breeze). Audible sounds have frequencies in the range of 20 Hz to 20 000 Hz, and these frequencies can be detected by humans. Ultrasonic sounds have frequencies greater than 20 000 Hz. These frequencies are used extensively in medical diagnostics. Elephants are capable of hearing infrasonic sounds. Sound waves move through different media, which causes them to have different speeds. The speed of sound through a medium is affect by the characteristics of the medium. The Speed of Sound The speed of sound travels quickly within a solid because a solid consist many particles that are closely packed together. In air, the particles are further apart from each other, so sound travels at a slower speed. VS. The stiffness in a medium can also affect the speed of a wave.
The stiffer the medium is, the faster a wave will propagate in it. Standing Waves A standing wave is a vibration of a system in which some particular points remain fixed (node) while others between them vibrate with the maximum amplitude (antinode). Resonance is defined as the increase in amplitude of a wave due to the transfer of energy in phase with the natural frequency of the wave One beat is defined as one louder than normal and one softer than normal sound.
Beats are special cases of interference that occurs when two sounds of slightly different frequency are played simultaneously.
The number of beats heard per second is called the beat frequency; and when the frequency is zero, the sound is tuned.
The calculation for determining the beat frequency: f beat= | f1 – f2|. Beats Types of Sound Waves The waves that do have harmonics, their harmonics are either odd or even. Even harmonics are normally known to be stable, smoother and comforting. Old harmonics are generally labelled as more unpleasant, unsteady, and sometimes disturbing. Fundamental frequency is known the lowest frequency produced by a particular instrument. It is also referred to the first harmonic in an instrument. Frequencies that are part of the harmonic series above the fundamental note are known as overtones. Fundamental Frequency Closed pipe Instruments Mechanical Reed Lip Reed Air Reed Recorder and flutes are both great examples of open pipe instruments. The reason why is because at both ends of the instrument, there is an opening that allows air to move around freely. Since the air are relatively free at both ends of the column, in order for standing wave patterns to be created, both ends of the air column must be a displacement antinode. If you were to see a standing wave pattern in an opened pipe, you’ll see antinodes at the ends of the pipe and a node in the middle of the pipe. The trumpet and the clarinet are also good examples of closed pipe wind instruments, because the player’s lips prevent the air to flow freely. The air at the open end of the column can move around freely, but it is restricted at the closed end. Since there is an air column closed at one end, this relates to acoustic resonance. In order for standing wave patterns to produce in a closed pipe, the length of the pipe must be right, so the reflected wave can combine with the incident wave (the wave that encounter the boundary wave).In addition, the open end of the column must be a displacement antinode and the closed end must be a node. Instruments like the clarinet, saxophone and bagpipes all contain mechanical reed that can be set into vibration, caused by an air stream that is forced in the instrument by a musician/player. When air is blow into an instrument, the air causes the reed to vibrate up and down against the mouth piece, and it allows the air into the body of the instrument. Brass instruments like the trumpet, tuba and trombones use a lip reed instead of a mechanical reed. Even though the lips are not really reeds, they are an exception because when a musician buzzes his/her lips on the mouthpiece of the instrument, they provide the same frequency of airbursts as a mechanical reed.
There are also other wind instruments that rely on an air reed. For example flutes, recorders and organ pipes are instruments that need an air reed. Let’s take the recorder as an example. As a player blows air into the mouthpiece of a recorder, the air blown splits into two regions. One of the regions is the sharp edge just pass the hole located on the top of the mouthpiece. The other region is the body of the recorder. As the air moves down the tube, the reflected air pulses acts as a reed, forming standing waves that’s becomes musical sounds. The voice organ which is a part of the human body is responsible for the production of sound, usually in the form of speech or singing. The human voice organ consists of three aspects, actuator (lungs), vibrator (vocal cord) and resonator (vocal tract) to produce sound waves in a variety of complex patterns. In music, sound is the sensation we experience when our auditory nerves are stimulated by vibrating air molecules.
Each sound is produced by the cutting of the airstream by the vocal cord which is comprised of a fundamental frequency and a large number of overtones. When an individual sings, musical sounds are being produced, that musical sound possesses three distinct properties which are:
•Amplitude
•Frequency
•Timbre. Voice organs used by singers in the production of music The Actuator (lungs) The Vibrator (vocal cord) The Resonator (vocal tract) The actuator occupy most of the thoracic cavity and its left and right actuator rest on the diaphragm which separates the thoracic and the abdominal cavities. The actuator provides an enormous space for gas exchange with oxygen entering the body and carbon dioxide leaving.
When singing, the singer regulates the outflow of breath in other to sustain phonation over the duration of the musical phrase and this is accomplished by contracting the abdominal muscles slowly and evenly. The vibrator are composed of twin infoldings of mucous membrane stretched horizontally across the larynx. The larynx on the other hand is a cylindrical framework of cartilage which serves to support the vibrator. One function of the vibrator is that it vibrates the air coming from the actuator to form sound.
How loud a singer can be heard depends on the amplitude of their vocal cords. The greater the amplitude of the vibrations, the greater the amount of energy carried by the wave, and the more intense the sound will be. Vocal loudness is measured in decibels (dB). While singing, the voice pitch of the singer is determined by the frequency of their vocal cords. The resonator consists of the air passages above the larynx. It has two main cavities, which are: the nasal cavity and the oral cavity. One of its many functions is that it protects the airway from particles that might either block it or injure it.
The resonator may be thought of as a peculiar megaphone which transmits sound from the 'voice box' into the air outside the singer's mouth. Sound coming from the larynx or the various timbres of different vowel sounds is not enough for a singer to be heard. Without the resonator only a buzzing sound would be heard Tension of strings Increasing the tension would result in a higher frequency, where a higher frequency would bring about a higher pitch or note What makes them different? The way it's used Length of strings When doing this, the length of the string shortens, which results in shorter wavelengths, therefore higher frequency or pitch.
Where players press their fingers at certain points of the fingerboard to change the note or pitch The body String instruments are specifically made in order for resonance to occur For example, the sound waves hit the inside of a guitar at its resonant points, allowing the music to be heard even louder than it have sounded with just the strings The first picture is of the inside of a guitar, where the top ridges resonate higher frequencies, while the bottom ridges resonate lower frequencies.
The second picture is a holographic picture of the waves produced in the body of the guitar at different frequencies, where the lighter parts are the nodes and the darker lines are the disturbance in the medium, caused by the waves Other Properties Bowed Instruments Vibrations of the strings are caused by friction present when the bow is dragged across the strings
Where friction comes, also come heat. The heat causes the horse hairs of the bow to lose friction, which prevents the strings to vibrate
The player must rub a substance called rosin on the bow which increases the friction, although too much rosin will result in the force of friction being higher than the force of the player’s arm, also preventing vibrations of the strings to occur. Electric Guitars Electric guitars produce sound by picking up vibrations of the strings and are converted into an electromagnetic signal. They are passed through an amplifier to increase the sound and a speaker to convert the electrical energy back into sound. Microphones, amplifiers, and speakers are used, which allows thousands of people to hear the performers Sound reinforcement system A microphone is a device that converts a form of energy into another, for in this case, converts the music produced by the instruments and singers into electronic signals.The microphone consists a diaphragm that possesses a electro-magnetic field, which moves in tune with the sound waves passing through, then creating an electric signal. This signal is then sent to an amplifier to make the music louder by increasing the strength, so that the thousands of people may listen to the performers clearly and loudly. Without the amplifier, very few people can hear the music, much less, the cheers and yelling of the audience will overpower the music played. Then, there are also the speakers, in which it’s main job is to convert the louder/amplified signal into sound waves that will distribute the music equally and clearly to the audience. Going back, the Greeks and Romans of the ancient times, have been the beginning of a long road of creations by applying many of the discovered theories to making concert theatres. An example of the first creations is the Teatro d’Argentina in Rome. A more recent and improved theatre is the Sydney Opera House. The sound waves of the source have all sorts of different patterns to move in a room. Also, the sound waves can undergo reflection (bouncing off surface), absorption (surface absorbs sound), diffraction and diffusion (bends or shatters around the surface), depending on the properties of the surface. Therefore, architects have carefully created theatres in which all components occur equally to create the right sound. Another phenomenon is reverberation, which is the amount of energy that remains after the source has stopped making sound energy, and the time it takes for it to decay. Equation: Rtime=0.016xV/A (V is for volume and A is area of absorption) A musical theatre is similar to an enormous resonator, for when the sound hits the surface of the room at it’s resonant frequency, the sound will change. Therefore, architects have applied this theory, which resulted in the creations of dome shaped theatres that would alter or control the sound in a specific way. The studies of physics have contributed to all of the works of humans for when it is related to music and will continue to contribute, resulting in even better musical technology and practices The End If you raise your soft pallet, you're opening up your throat. Try it out, and you'll feel your throat opening wider. This allows more air passage, and for more complex notes to come out. It also helps with the development of louder and stronger notes
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