In this particular paper, we are going to present the key ideas that have been described by Mr. Protik Majumder in his youtube video ‘Musical Acoustics and Sound Perception’. This lecture of his addresses the dynamics of sound synthesis and in short, Mr. Majumder also explains the semantics of our ability to identify and distinguish one sound from the other.
He starts off by plucking a string and showing the audience how a sound wave is created. Using this concept, he describes some key concepts including transverse waves, the energy of the wave and he shows the shape of the wave and explains that in a transverse wave, the direction of propagation is perpendicular to the movement of energy. He first creates a fundamental wave which comprises of only a single wave cycle. He then creates a second harmonic by propagating a wave that has two repetitions in a single wave. He then goes forth to create the third harmonic and describes that as we move on to create more propagations in a single wave, the frequency continues to shorten. In musical instruments he describes, we create sound in a similar fashion by plucking them, blowing through them or striking them. The frequency of the sound depends upon the nature of the material that they are created through, their length and many other properties of the instrument like the tightness and the length in case of a string.
Following the description of sound as a wave, Mr. Majumder becomes a little more focused towards the nature of the sound wave. He uses the model of the spring by increasing the pressure in some parts of the string, so that other areas are lower in pressure. This type of wave he describes is a longitudinal wave like every type of sound wave. He then translates all of these concepts into music and links the pitch of any musical instrument to the frequency of the sound and the musical intervals to the ratio of the frequency.
So if we go from a first harmonic wave to the second harmonic, the frequency doubles and in music, it results in the creation of an ‘octave’. Using the same example as the one professor uses, going from 100Hz of frequency to 200Hz would create an octave. So ultimately, we hear these ratios as the musical sounds. So moving in between the second and the third harmonic would create a perfect fifth while the movement in between the fourth and the third harmonic would give us a perfect fourth.
The professor also highlights that in our attempts in distinguishing one sound from the other, the pitch is not everything. For if it was, we would not be able to make this distinction. He shows the audience an oscillation diagram that results from the striking of a tuning folk. The same experiment with a French horn on a ‘middle C’ note like the tuning folk creates basically the same oscillatory diagram which is a little more complex with smaller oscillations within the wave itself. He then makes audio demonstrations and test the students to see the point at which they are going to identify the sound starting with the building up of the sound harmonic by harmonic.
He then uses the cross-section of the ear and zooms in on the cochlea to show how that part of the ear detects the sound at different frequencies. These frequencies he says excites specific regions of the basilar membrane within the ear cochlea and helps in distinguishing of the sound.
He then records the oscillatory diagrams for the sounds that he makes the same note and frequencies but reciting different vowels being ‘aaaaaaaa’, ‘eeeeee’, ‘oooooo’ and we can see that the complexity of these oscillations is different from one another.
The professor overall uses very practical and effective examples to help his students understand the use of sounds in the creation of music and through many visual and audio demonstrations, we keep the attention through the entire 25 minutes and 38 seconds of the video. It was the effectiveness of all of these techniques that led to a clearer understanding.
Works Cited
Williams College. Musical Acoustics and Sound Perception. Massachusetts, 15 August 2011.
