Beat frequency Definition and 69 Threads

In acoustics, a beat is an interference pattern between two sounds of slightly different frequencies, perceived as a periodic variation in volume whose rate is the difference of the two frequencies.
With tuning instruments that can produce sustained tones, beats can be readily recognized. Tuning two tones to a unison will present a peculiar effect: when the two tones are close in pitch but not identical, the difference in frequency generates the beating. The volume varies like in a tremolo as the sounds alternately interfere constructively and destructively. As the two tones gradually approach unison, the beating slows down and may become so slow as to be imperceptible. As the two tones get further apart, their beat frequency starts to approach the range of human pitch perception, the beating starts to sound like a note, and a combination tone is produced. This combination tone can also be referred to as a missing fundamental, as the beat frequency of any two tones is equivalent to the frequency of their implied fundamental frequency.

View More On Wikipedia.org
Recent contents Top users
  1. T

    Calculating Beat Frequency of 3 Frequencies

    Homework Statement If there are three frequencies: 200hz, 206hz and 209hz, how do you calculate the beat frequency of three frequencies? Homework Equations Fb=abs(F1-F2) The Attempt at a Solution
  2. M

    Calculating the Frequency of a Car Horn Using the Doppler Effect

    Two automobiles are equipped with the same single-frequency horn. When one is at rest and the other is moving toward an observer at 13 m/s, a beat frequency of 5.8 Hz is heard. What is the frequency the horns emit? Assume T = 20°C. I understand that this is related somehow to the doplar...
  3. C

    Calculating Beat Frequency in Ultrasound Reflection from Moving Bloodstream

    Homework Statement Ultrasound reflected from an oncoming bloodstream that is moving at 38 cm/s is mixed with the original frequency of 1.3 MHz to produce beats. What is the beat frequency? (Velocity of sound in blood = 1540 m/s.) Homework Equations Fo=Fs(v+Vo/v) Fb- (F2-f1) The...
  4. B

    Why Analyze Negative Beat Frequencies if They Don't Exist?

    The equation for beat frequency is as follows: f_b = |f_2 - f_1| Meaning the absolute value of the difference between 2 frequencies. But when you figure out the possiblilities of f_2, you analyze both -f_b and f_b, if you are using the absolute value because negative beat frequencies...
  5. P

    What Causes Standing Waves and Beat Frequencies in Sound?

    Which one of the following situations could result in a standing wave? A- Two waves with different frequencies moving in the same direction. B- Two waves with different frequencies moving in opposite direction. C- Two identical waves moving in opposite directions D- Two identical waves...
  6. Amith2006

    How Many Beats Are Heard When Three Tuning Forks Are Sounded Together?

    Sir, Three tuning forks of frequencies 100Hz,101Hz and 102Hz are sounded together. How many beats will be heard in one second? If 2 forks are sounded together then the number of beats heard will be equal to the difference of their frequencies. But I don't know how to calculate the beat...
  7. A

    Beat Frequency Chart: Solve Problems & Find Original Freq.

    I've posted a few threads on beat frequency, but I still need help. I know that it's really simple, and once I get it I'm going to kick myself for being so stupid, but it just won't get through my head. I made a chart to help me figure out which possibility is the original one in beat...
  8. A

    Another Beat Frequency Question

    I have another beat frequency question. I understand how to get the possible frequencies of a string or tuning fork, but I don't know how to determine which one is the original frequency. When a guitar string is sounded against a 440 Hz tuning fork, twelve beats are heard in two seconds. a)...
  9. A

    What is the original frequency and how can it be calculated?

    I need help with a couple of problems: A tuning fork of uknown frequency is sounded together with another tuning fork of 630 Hz. Seven beats are noted when a weight is put on the uknown tuning fork. The beat frequency is noted to increase. What is the original frequency? A cottager lying...
  10. B

    Investigating Beat Frequency in Pipes with Different Temperatures

    Two pipes, equal in length, are each open at one end. Each has a fundamental frequency of 473 Hz at 297 K. In one pipe the air temperature is increased to 302 K. If the two pipes are sounded together, what beat frequency results? I think I missed this day entirely due to another project. I...
  11. F

    What are the possible lengths of organ pipes based on beat frequency?

    A friend in another city tells you that she has a pair of organ pipes, one open at both ends, the other open at one end only. In addition, she has determined that the beat frequency caused by the second-lowest frequency of each pipe is equal to the beat frequency caused by the ninth-lowest...
  12. B

    Solving Beat Frequency Woes: Physics Exam Prep

    So I'm studying for my Physics exam tommorow and the damned Sound unit seems to always give me problems. Anyway I'm doing a review question relating to Beat Frequency and I just can't seem to figure out what to do. Here is the question and my sad attempt at it. When a violin string is...
  13. F

    Beat frequency of Two in-phase loudspeakers

    4. Two in-phase loudspeakers are some distance apart. They emit sound with a frequency of 536 Hz. A microphone is moved between the speakers along the line joining the two speakers with a constant speed of 1.60 m/s. What beat frequency is observed? The speed of sound in air is 343 m/s. Could...
  14. T

    How does the beat frequency change when the mirror's speed is much smaller than the speed of light?

    There are two parts to this but i solved the first part: in part a) i was to show, for an electomagnetic wave reflected back to its source from a mirror approaching at speed v, that the reflected wave had frequency f=f_{source}\frac{c+v}{c-v} where fsource is the source frequency and c is the...
  15. C

    What Causes the Pulsating Sound from a Jet's Engines?

    Finally, your friend's twin engine jet airplane lands. As it stands on the runway, you hear the sound of the engines getting louder and softer, rhythmically once every two seconds. The average frequency you hear is 4100 Hz. What is the difference between the individual frequencies of the sounds...
  16. C

    What is the blood beat frequency?

    Ultrasound reflected from an oncoming bloodstream that is moving at a 30 cm/s is mixed with the original frequency of 2.5 MHz to produce beats. What is the beat frequency? (Velocity of sound in blood = 1540 m/s.) Beat Frequency in Hz =
  17. T

    Beat Frequency: How Does it Change With Pure Tone Increase?

    if i play two pure tones together, i create a beat frequency. if i increase, any of the two pure tones, what happens to the beat frequency? heres my logic as to why the beat frequency can go either way: Fb = F1-F2, so if you increase F1 it increases and the opposite if you increase F2...
  18. J

    How Do Doppler Effects Determine the Frequency of a Whistle in Motion?

    A Boy is walking away from a wall at a speed of 1m/s in a direction at right angles to the wall. As he walks, he blows a whistle steadily. An observer toward whom the boy is walking hearts 4 beats per second. If the speed of sound is 340 m/s, what is the frequency of the whistle? My...
  19. J

    Calculating Beat Frequency in Ultrasound Doppler Effect

    I have been trying this problem for a couple of days: Ultrasound reflected from an oncoming bloodstream that is moving at 30 cm/s is mixed with the original frequency of 2.5 MHz to produce beats. What is the beat frequency? (Velocity of sound in blood = 1540 m/s.) I tried this as a...
Back
Top