17. SENSING THE SOUNDS

 17.      SENSING THE SOUNDS

The sound vibrations are detected in the ear, changed to electrical signals, and transmitted by the nerves to the brain, where they are processed and recorded. The characteristics of sound include pitch and loudness. It is also possible to determine the direction and distance from what we hear. Sounds provide information about the environment around us.

How ear works

The ear is the sense organ that detects sound waves and sends those signals to the brain for processing. The way the ear works is that sound waves vibrate the eardrum, just inside the ear. The eardrum sends waves through a fluid inside a narrow tube called the cochlea, which in turn vibrates tiny hairs that are tuned to the different pitches of the sound. Information from the vibration of the hair stimulates nerves which send the signals to the brain for processing.

Similarity to microphone

The way the ear works is similar to the way a microphone works, where sound vibrates a diaphragm, which causes electrical signals to travel through a wire, to a circuit card for processing. The operation of the ear is much more complex. But it is much more flexible and does not require batteries.

Sound characteristics and sensing the sounds.

The sound we hear has both pitch and loudness. We gather information by sensing and processing waveforms with these characteristics.

Pitch

A normal human can hear between 20 Hz and 20,000 Hz. That is quite a range. 20 Hz is a very low pitch sound or very deep tones. 20,000 Hz is a high pitch sound. Besides hearing low frequencies, we can often feel them. An example of that is when we can feel the bass from a loudspeaker. When humans get older, they have trouble hearing high-pitched sounds and their detection range diminishes.

The normal frequency range that a 5-octave keyboard with 61 keys is about 60 Hz to 2000 Hz. The speaking range is around 200 Hz and the shouting range is around 500 Hz.

The more bass a voice is, it has less frequency and the more treble a voice is, it has more frequency. The bass or treble can be adjusted to a certain extent with the help of an amplifier, and also gain in volume with some special effects shall be obtained.

Changing Pitch

·         A string vibrates with a particular fundamental frequency. It is possible to produce pitches with different frequencies from the same string. The four properties of the string that affect its frequency are length, diameter, tension, and density. These properties are described below:

·         When the length of a string is changed, it will vibrate with a different frequency. Shorter strings have a higher frequency and therefore higher pitch. When a musician presses the finger on a string, the length of the string is shortened with increasing pitch.

·         Diameter is the thickness of the string. Thick strings with large diameters vibrate slower and have lower frequencies than thin ones. A thin string with a 10 millimeter diameter will have a frequency twice as high as one with a larger, 20 millimeter diameter. This means that the thin string will sound one octave above the thicker one.

·         A string stretched between two points will have tension. Tension refers to how tightly the string is stretched. Tightening the string gives it a higher frequency while loosening it lowers the frequency. When string players tighten or loosen their strings, they are altering the pitches to make them in tune.

·         The density of a string will also affect its frequency. Remember that dense molecules vibrate at slower speeds. The denser the string is, the slower it will vibrate, and the lower its frequency will be. Instruments often have strings made of different materials. The strings used for low pitches will be made of a more dense material than the strings used for high pitches.

Loudness

The amplitude of a sound wave determines its loudness. There is a minimum amplitude required for us to hear a sound. Amplitude varies with the species of animal. Sounds that are too loud can injure the ear and result in loss of hearing.

Loudness is measured in decibels, which really measures the energy of the sound. Every 10 decibels increases the energy by 10 times. In other words, 20 decibels have 10 times the energy of 10 decibels, and 30 decibels have 100 times that of 10 decibels. A human can hear from very quiet sounds at 0.1 decibels to sounds at 120 decibels, which actually can cause pain. At the high end of the scale, the energy can cause damage to the sensitive membranes in the ear. Animals and humans can hear sounds in limited volume or amplitude. Some animals can hear sounds that humans can’t.

The correct loudness or volume is necessary for the sound to be audible and clear and thereby correct interpretation of the information or words or sounds that are shared.

Direction and distance

We can detect the direction a sound is coming from and, in some cases, its distance. The detection of direction is determined by comparing the sound heard by each ear. The detection of distance is more difficult and often relates to the loudness and quality of the sound heard.

Also, if we are focusing the sound to be heard in a particular direction, then the speakers should be placed in that direction. And speakers should not be facing towards the microphone that is connected to it, to avoid feedback and noise. 

17.1.        EQUALIZATION CHART:

17.2.     MANDRA STAAYI VARISAI:

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