In this lecture we are going to learn about the characteristics of musical sound, the definition of sound, and how sounds work. So let’s start with the definition of sound and then we will see the most important characteristics of musical sound in detail.
What is sound
Sound is a vibration in an elastic medium with definite frequency and intensity which can be heard by the human ear.
On the basis of frequency f, sound waves are classified into three types:
| 1. | Infrasound | f < 20 Hz |
| 2. | Audible Sound | 20 Hz < f < 20 KHz |
| 3. | Ultrasound | f > 20 KHz |
The audible sound also can be classified into two categories. The categories are discussed below.
Classification of Audible Sound
The two categories of audible sounds are:
- Musical Sound
- Noise
1. Musical Sound
- The sound which produces a pleasing effect on the ear is called musical sound.
- Examples: Sound produced by musical instruments like sitar, violin, flute, piano, etc.
Properties of Musical Sound
- Musical sound is characterized by the following properties:
- The musical sound waveforms are regular in shape.
- They have definite periodicity.
- They do not undergo a sudden change in amplitude.
2. Noise
- The sound that produces a jarring effect on the ear and is unpleasant to hear is called noise.
- Example: Sound produces by flying airplanes, road traffic, crackers, etc.
Properties of Noise
Noise is characterized by the following properties:
- Noise waveforms are irregular in shape.
- They do not have definite periodicity.
- They undergo a sudden change in amplitude.
Now we will learn about the most important topic of this lecture which is the Characteristics of Musical Sound. This is very important for the students to understand the concept of musical sounds and how they work.
Also Read: Distinguish Between Loudness and Intensity of Sound
Characteristics of Musical Sound
The characteristics of musical sounds are:
| Pitch | Related to the frequency of sound |
| Loudness | Related to the intensity of sound |
| Timbre | Related to the quality of sound |
Pitch
- It is a sensation that depends upon the frequency. Pitch helps in distinguishing between a note of high-frequency and low-frequency sound (i.e., it helps to distinguish a shrill sound from a flat sound) of the same intensity produced by the same musical instruments. A shrill sound is produced by a sound of high frequency.
- The sound produced by ladies and children is of high pitch type because the frequency is high. Similarly, the sound produced by a bee or mosquito is of high pitch due to high frequency.
- Thus, the greater the frequency of a sound the higher the pitch and vice versa. The pitch of sound changes due to Doppler’s principle when either the source or the observer or both are in motion.
Loudness
- Loudness is a characteristic that is common to all sounds, whether classified as musical sound or noise.
- Loudness is a degree f sensation produced in the ear. Thus, loudness varies from one listener to another. Loudness depends upon the intensity and also upon the sensitivity of the ear.
- Loudness and intensity are related to each other by the relation
\mathbf{L \propto \log_{10}I}
or, \mathbf{L = K \log_{10}I}, Where K is contant.
- From this relation, it is seen that loudness is directly proportional to the logarithm of intensity, and is known as Weber-Fechner Law.
- From the above equation,
\mathbf{\frac{dL}{dI}=\frac{K}{I}}
- where\mathbf{\frac{dL}{dI}} is called sensitiveness of ear. Therefore, sensitiveness decreases with increases in intensity. Loudness is a physiological quantity.
Timber
- It is the quality of sound which enables us to distinguish between two sounds having the same loudness and pitch. It depends on the presence of overtones.
- It helps us to distinguish between musical notes emitted by different musical instruments and vices of different persons even though the sound has the same pitch and loudness.
Also Read: Factors Affecting Acoustics of Building and Their Remedies
FAQs
What is the definition of sound in physics?
Sound is a pressure wave that is created by a vibrating object.
What are the three characteristics of musical sound?
loudness. pitch or shrillness, and. quality or timbre.
What is the sound and SI unit of sound?
The SI unit of sound or more precisely frequency is hertz denoted by Hz.
What are the different types of musical sounds?
Pure tones, harmonics, periodic and non-periodic sounds; Timbre, spectrum, envelope, and transients.
