Important Topic of Physics: Beats

# Important Topic of Physics: Beats

Table of Contents

## Introduction:

The pulsation is caused by the combination of two waves of slightly different frequencies in physics. Strike a white key and an adjacent black key at the bass end of the keyboard to demonstrate the beats for sound waves principle. The resulting sound is alternately soft and loud, with distinct pulsations or throbs known as beats. The beat frequency increases toward the treble end of the keyboard because the frequency difference between adjacent keys is greater than at the lower end. The figure depicts two waves, n 1 and n 2 , with frequencies of 24 and 30 vibrations per second (hertz), respectively; the beat frequency N is their difference, 6 beats per second.

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The phenomenon of beats is used in a variety of ways. In instrument tuning, for example, if a tuning fork and a piano key of the same note are struck simultaneously and no beat is heard, they are of the identical pitch. Ultrasonic vibrations (having a frequency higher than that of audible sound), such as bat and dolphin vocal sounds, can be detected by superimposing a sound of a different frequency to produce audible beats. The principle is also used in superheterodyne radio wave reception, which involves beating a low-frequency signal from an oscillator against an incoming high-frequency radio signal to produce an intermediate (beat) a frequency that can be amplified into audible signals

## Overview:

A beat is an interference pattern between two slightly different frequencies of sound, perceived as a periodic variation in volume whose rate is the difference between the two frequencies. With tuning devices capable of producing sustained tones, beats can be easily identified. When two tones are tuned to a unison, a strange effect occurs: the difference in frequency causes the thumping when the two tones are near in pitch but not identical. The volume changes like a tremolo as the sounds alternately interfere constructively and destructively. The thumping slows down as the two tones approach unity, and it may eventually become unnoticeable. As the beat frequency of the two tones approaches that of human pitch perception, the beating begins to sound like a note, and a combination tone is generated at the keyboard’s very end.

Both frequencies are nearly equal, and there is no discernible difference in the audible frequency you hear when you play them separately; yet, when played together, these two frequencies interfere with one another due to their close proximity in frequency. Their crest-to-crest interference creates constructive interference, which increases the amplitude of the wave and thus the volume of the sound. When a crest and trough collide, the interference produced is destructive, so they both cancel out, and the amplitude produced is zero; thus, the loudness is reduced to zero. The difference between the two is equivalent to the beat frequency, which is the frequency at which the loudness increases and lowers.

### Binaural beats:

Binaural beats are two types of beats that have different frequencies heard in each ear. To understand the difference in frequencies, our brain processes the difference between these two beats. When two separate pure-tone sine waves, both with frequencies lower than 1500 Hz and less than a 40 Hz difference between them, are dichotically given to a listener, a binaural beat is felt (one through each ear).

The inferior colliculus of the midbrain and the superior olivary complex of the brainstem are where auditory signals from each ear are combined and electrical impulses are precipitated along neural pathways through the reticular formation up the midbrain to the thalamus, auditory cortex, and other cortical regions, resulting in binaural-beat perception.

Reduced stress, anxiety, increased attention, increased concentration, higher motivation, enhanced confidence, and deeper meditation are some of the purported benefits of binaural beats therapy. However, there is no proof to back up those who promote the alleged benefits’ claims. Because studies on the clinical effects of binaural beat therapy are ambiguous, it is advisable not to use this form of intervention to replace established stress and anxiety treatments until conclusive evidence is produced.

### Beat Frequency:

When two sound waves of different frequencies collide, their amplitudes are added and subtracted alternately over a predetermined time period to produce the beat frequency. As a result, the sound gradually becomes louder and weaker. Beats are formed when two waves with nearly identical frequencies travelling in the same direction collide at a point. When two sound waves with different frequencies approach your ear, the alternating productive and harmful interference causes the sound to alternately be loud and soft. This is referred to as beating. The beat frequency is equal to the sum of the frequency differences between the two waves. The beat frequency is the number of beats per second that equals the frequency difference between two waves. Beat frequency formula is,

f b= |f 2-f 1|

### Occurrence of Beat:

Beats occur when two waves of similar frequencies overlap and combine to form a new wave. Let us conduct an experiment to better understand this phenomenon.

We’ll need two tuning forks with similar frequencies, such as 700 Hz and 705 Hz.

Both frequencies are nearly identical, and there is no discernible difference in the audible frequency you hear when you play them separately; however, when played together, these two frequencies interfere with each other due to their frequency proximity. Their crest-to-crest interference produces constructive interference, increasing the amplitude of the wave and thus the loudness of the sound. When a crest and a trough collide, the interference produced is destructive; thus, they both cancel out, and the amplitude produced is equal to zero; thus, the loudness is reduced to zero; the frequency at which the loudness increases and decreases is known as the beat frequency; this beat frequency is equal to the difference between the crest and the trough.

In our case, frequency A is 700 Hz and frequency B is 705 Hz; thus, if these two frequencies coincide in time, the resultant beat frequency is 705-700 Hz = 5 Hz. By listening to the beats of two close frequencies, we can determine the difference between them; the closer the two frequencies are, the smaller the resultant frequency. The beats would eventually fade away. Piano tuners use this beats and interference technique to finely tune piano wires; they pluck the wire and a tuning fork at the same time, and then tighten or loosen the wire tension to increase or decrease the frequency, thereby tuning the wire to the same frequency as the fork.

The term “beat” refers to sound waves. The beat frequency is the frequency difference between two waves. It’s due to both constructive and destructive interference. In sound, we hear the beat frequency as the rate at which the loudness of the sound varies, whereas the ordinary frequency of the waves is heard as the pitch of the sound. In this section, we go over the concept of beat frequency and the beat frequency formula in depth. A binaural beat is an auditory illusion that occurs when two different pure-tone sine waves, both with frequencies lower than 1500 Hz and a difference of less than 40 Hz, are presented to a listener dichotically (one through each ear).

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## Frequently Asked Questions (FAQs):

Question: What is the origin of all noises?

Answer: Vibrations are the source of all sounds. When sound waves travel through air molecules, the molecules vibrate, resulting in sound.

Question: These vibrations travel through the air and eventually reach our eardrums. How many different kinds of sounds are there?

Answer: There are two kinds of sound: audible sound and inaudible sound.

Sounds with frequencies ranging from 20 Hz to 20 kHz are considered audible, while sounds that the human ear cannot detect are considered inaudible. Infrasonic sound is defined as sound with a frequency of less than 20 hertz. Ultrasonic sound is defined as sound with a frequency greater than 20 kHz. If the frequency of the sound wave is above 20 kHz, it is known as ultrasonic sound.

Question: What exactly are binaural beats?

Answer: Binaural beats are two types of beats that have different frequencies heard in each ear. To understand the difference in frequencies, our brain processes the difference between these two beats.

Question: Are binaural beats harmful?

Answer: Binaural beats are risky because they can cause noise-induced hearing loss. This is an auditory phenomenon that occurs when the eardrum ruptures or the middle bone in the ear is damaged.

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