Identifying FrequenciesIdentifying Frequencies

Terms:Terms:

LoudnessLoudness

PitchPitch

TimbreTimbre

LoudnessLoudnessSound loudness is a subjective term describing the strength Sound loudness is a subjective term describing the strength of the ear's perception of a sound. of the ear's perception of a sound.

It is intimately related to sound intensity but can by no It is intimately related to sound intensity but can by no means be considered identical to intensity. The sound means be considered identical to intensity. The sound intensity must be factored by the ear's sensitivity to the intensity must be factored by the ear's sensitivity to the particular frequencies contained in the sound. particular frequencies contained in the sound.

This is the kind of information contained in equal loudness This is the kind of information contained in equal loudness curves for the human ear. It must also be considered that curves for the human ear. It must also be considered that the ear's response to increasing sound intensity is a "power the ear's response to increasing sound intensity is a "power of ten" or logarithmic relationship. of ten" or logarithmic relationship.

This is one of the motivations for using the decibel scale to This is one of the motivations for using the decibel scale to measure sound intensity. A general "rule of thumb" for measure sound intensity. A general "rule of thumb" for loudness is that the power must be increased by about a loudness is that the power must be increased by about a factor of ten to sound twice as loud. factor of ten to sound twice as loud.

http://hyperphysics.phy-astr.gsu.edu/Hbase/sound/loud.html

A widely used "rule of thumb" for the loudness A widely used "rule of thumb" for the loudness of a particular sound is that the sound must be of a particular sound is that the sound must be increased in intensity by a factor of ten for the increased in intensity by a factor of ten for the sound to be perceived as twice as loud. sound to be perceived as twice as loud.

A common way of stating it is that it takes 10 A common way of stating it is that it takes 10 violins to sound twice as loud as one violin. violins to sound twice as loud as one violin. Another way to state the rule is to say that the Another way to state the rule is to say that the loudness doubles for every 10 loudness doubles for every 10 phonphon increase increase in the sound loudness level. in the sound loudness level.

Although this rule is widely used, it must be Although this rule is widely used, it must be emphasized that it is an approximate general emphasized that it is an approximate general statement based upon a great deal of statement based upon a great deal of investigation of average human hearing but it investigation of average human hearing but it is not to be taken as a hard and fast rule.is not to be taken as a hard and fast rule.

Two different 60 decibel sounds will not in general Two different 60 decibel sounds will not in general have the same loudnesshave the same loudness

Saying that two sounds have equal intensity is not Saying that two sounds have equal intensity is not the same thing as saying that they have equal the same thing as saying that they have equal loudness. Since the human hearing sensitivity loudness. Since the human hearing sensitivity varies with frequency, it is useful to plot equal varies with frequency, it is useful to plot equal loudness curves which show that variation for the loudness curves which show that variation for the average human ear. average human ear.

If 1000 Hz is chosen as a standard frequency, then If 1000 Hz is chosen as a standard frequency, then each equal loudness curve can be referenced to the each equal loudness curve can be referenced to the decibel level at 1000 Hz. This is the basis for the decibel level at 1000 Hz. This is the basis for the measurement of loudness in phons. If a given sound measurement of loudness in phons. If a given sound is perceived to be as loud as a 60 dB sound at 1000 is perceived to be as loud as a 60 dB sound at 1000 Hz, then it is said to have a loudness of 60 phons.Hz, then it is said to have a loudness of 60 phons.

Fletcher-Munson CurveFletcher-Munson Curve

Estimating Changes in LoudnessEstimating Changes in Loudness

There are variations in individual perception of There are variations in individual perception of the strength of sound and studies have shown the strength of sound and studies have shown that in general the sound is perceived twice as that in general the sound is perceived twice as loud if the sound level increases by 10 dB. loud if the sound level increases by 10 dB.

Similarly, a 20 dB increase in the sound level is Similarly, a 20 dB increase in the sound level is perceived as four times as loud by the normal perceived as four times as loud by the normal human ear.human ear.

Changing 1 dB in sound pressure level - Insignificant Changing 1 dB in sound pressure level - Insignificant change in apparent loudnesschange in apparent loudness

Changing 3 dB in sound pressure level - Just Changing 3 dB in sound pressure level - Just perceptible change in apparent loudnessperceptible change in apparent loudness

Changing 5 dB in sound pressure level - Clearly Changing 5 dB in sound pressure level - Clearly noticeable change in apparent loudnessnoticeable change in apparent loudness

Changing 10 dB in sound pressure level - Twice or Changing 10 dB in sound pressure level - Twice or half as loudhalf as loud

Changing 15 dB in sound pressure level - Significant Changing 15 dB in sound pressure level - Significant change in apparent loudnesschange in apparent loudness

Changing 20 dB in sound pressure level - Much Changing 20 dB in sound pressure level - Much louder or quieter, four times as loudlouder or quieter, four times as loud

PitchPitch

Pitch = frequency of soundPitch = frequency of sound

For example, middle C in equal temperament = For example, middle C in equal temperament = 261.6 Hz261.6 Hz

Sounds may be generally characterized by pitch, Sounds may be generally characterized by pitch, loudness, and quality. The perceived pitch of a loudness, and quality. The perceived pitch of a sound is just the ear's response to frequency, i.e., sound is just the ear's response to frequency, i.e., for most practical purposes the pitch is just the for most practical purposes the pitch is just the frequency. frequency.

TimbreTimbreColor, or timbre (pronounced "TAM-ber"). Timbre describes all of the aspects of a Color, or timbre (pronounced "TAM-ber"). Timbre describes all of the aspects of a musical sound that do not have anything to do with the sound's pitch, loudness, or musical sound that do not have anything to do with the sound's pitch, loudness, or length. In other words, if a flute plays a note, and then an oboe plays the same note, length. In other words, if a flute plays a note, and then an oboe plays the same note, for the same length of time, at the same loudness, you can still easily distinguish for the same length of time, at the same loudness, you can still easily distinguish between the two sounds, because a flute sounds different from an oboe. between the two sounds, because a flute sounds different from an oboe.

This difference is in the timbre of the sounds. This difference is in the timbre of the sounds.

Timbre is caused by the fact that each note from a musical instrument is a complex Timbre is caused by the fact that each note from a musical instrument is a complex wave containing more than one frequency. For instruments that produce notes with wave containing more than one frequency. For instruments that produce notes with a clear and specific pitch, the frequencies involved are part of a harmonic series. For a clear and specific pitch, the frequencies involved are part of a harmonic series. For other instruments (such as drums), the sound wave may have an even greater other instruments (such as drums), the sound wave may have an even greater variety of frequencies. variety of frequencies.

We hear each mixture of frequencies not as separate sounds, but as the color of the We hear each mixture of frequencies not as separate sounds, but as the color of the sound. Small differences in the balance of the frequencies - how many you can hear, sound. Small differences in the balance of the frequencies - how many you can hear, their relationship to the fundamental pitch, and how loud they are compared to each their relationship to the fundamental pitch, and how loud they are compared to each other - create the many different musical colors. other - create the many different musical colors.

The harmonics at the beginning of each note - the attack - are especially important The harmonics at the beginning of each note - the attack - are especially important for timbre, so it is actually easier to identify instruments that are playing short notes for timbre, so it is actually easier to identify instruments that are playing short notes with strong articulations than it is to identify instruments playing long, smooth with strong articulations than it is to identify instruments playing long, smooth notes.notes.

The human ear and brain are capable of hearing and The human ear and brain are capable of hearing and appreciating very small variations in timbre. appreciating very small variations in timbre.

A listener can hear not only the difference between an oboe A listener can hear not only the difference between an oboe and a flute, but also the difference between two different and a flute, but also the difference between two different oboes. oboes.

The general sound that one would expect of a type of The general sound that one would expect of a type of instrument - a trombone for example - is usually called its instrument - a trombone for example - is usually called its timbre or color. Variations in timbre between specific timbre or color. Variations in timbre between specific instruments - two different trombones, for example, or two instruments - two different trombones, for example, or two different trombone players, or the same trombone player different trombone players, or the same trombone player using different types of sound in different pieces - may be using different types of sound in different pieces - may be called differences in timbre or color, or may be called called differences in timbre or color, or may be called differences in tone or in tone quality. differences in tone or in tone quality.

Tone quality may refer specifically to "quality", as when a Tone quality may refer specifically to "quality", as when a young trombonist is encouraged to have a "fuller" or "more young trombonist is encouraged to have a "fuller" or "more focussed" tone quality, or it can refer neutrally to differences focussed" tone quality, or it can refer neutrally to differences in sound, as when an orchestral trombonist is asked to play in sound, as when an orchestral trombonist is asked to play with a "brassy" tone quality in one passage and a "mellow" with a "brassy" tone quality in one passage and a "mellow" tone quality in another.tone quality in another.

Many words are used to describe timbre. Some are somewhat interchangeable, and Many words are used to describe timbre. Some are somewhat interchangeable, and some may have slightly different meanings for different musicians, so no attempt will some may have slightly different meanings for different musicians, so no attempt will be made to provide definitions. Here are a few words commonly used to describe be made to provide definitions. Here are a few words commonly used to describe either timbre or tone quality.either timbre or tone quality.

Reedy Reedy

Brassy Brassy

Clear Clear

Focused or unfocussed Focused or unfocussed

Breathy (pronounced "BRETH-ee") Breathy (pronounced "BRETH-ee")

Rounded Rounded

Piercing Piercing

Strident Strident

Harsh Harsh

Warm Warm

Mellow Mellow

Resonant Resonant

Dark or Bright Dark or Bright

Heavy or Light Heavy or Light

Flat Flat

Having much, little, or no vibrato (a controlled wavering in the sound); or narrow Having much, little, or no vibrato (a controlled wavering in the sound); or narrow or wide, or slow or fast, vibrato or wide, or slow or fast, vibrato