1. The frequency range that the human ear can hear is 20-20KHZ.
2. The device that converts sound energy into electrical energy is a microphone.
3. The device that converts electrical energy into acoustic energy is a loudspeaker.
4, the audio system has an acoustic feedback howling, usually adjust the equalizer.
5, the room reverberation time is too long, there will be sound turbidity.
6, the room reverberation time is too short, there will be sound dry.
7, singing feels too dry, when adjusting the reverberator.
8. The voice is turbid when speaking. The possible reason is that the reverb effect is added.
9. The three elements of sound refer to sound intensity, pitch, and tone.
10. The objective evaluation scale corresponding to the sound intensity is the amplitude.
11. The objective evaluation scale corresponding to pitch is frequency.
12. The objective evaluation scale corresponding to the tone color is the spectrum.
13. The loudness of the human ear is related to the frequency of the acoustic vibration.
14. The relationship between the loudness and frequency of the human ear's perception of high sound pressure level sound is small.
15. The ear is most sensitive to the sound of the mid-range.
16. The human ear feels slower to the sound of high frequency and low frequency band.
17. The relationship between the loudness and frequency of the human ear to the low sound pressure level sound is very large.
18. Each curve in the equal-tone curve shows different sound pressure levels at different frequencies, but the human ear feels the same loudness.
19. In the equal-tone curve, the number marked on each curve indicates the loudness level.
20. The voltage gain formula for the amplifier expressed in decibels is 20 lg (output voltage / input voltage).
21. The unit of the loudness level is phon.
22. The dB value measured by the sound level meter indicates the weighted sound pressure level.
23. The tone is determined by the waveform of the sound being emitted.
24. The time required for the sound signal to drop by 60 dB from the steady state is called the reverberation time.
25. The basic elements of music are melody, rhythm, and harmony.
26. The maximum instantaneous value of the sound wave is called the amplitude.
27. The number of vibrations in one second is called the frequency.
28. If a sound sounds the same as the selected 1KHz pure tone, the sound pressure level of this 1KHz pure tone is defined as the loudness of the sound to be tested.
29, the human ear is most sensitive to the sound of 1~3KHZ.
30. The human ear is slower than the sound below 100Hz, and the sound above 8K.
31. The early reflections on both sides of the stage aggravate and thicken the original sound, which is a beneficial reflection sound.
32. The reflected sound on the back side of the auditorium acts as an echo to the original sound, which is a harmful reflection.
33. The sound travels in the air at a speed of about 340 m/s.
34. To make the stadium unable to hear two sounds from the main speaker about 34m, a delay of 0.1s should be added to the sound box near the audience.
35. A material with a small reflection coefficient is called a sound absorbing material.
36. A material with a small transmission coefficient is called a sound insulating material.
37. A material with a large transmission coefficient is called a sound-permeable material. î‹°
38. The fully sound absorbing material refers to the sound absorption coefficient α=1.
39. The total reflection material refers to the sound absorption coefficient α=0.
40. Rock wool, glass wool and other materials mainly absorb high frequency and medium frequency.
41. Polyurethane sound absorbing foam mainly absorbs high frequency and intermediate frequency.
42. The thin plate plus cavity mainly absorbs low frequency.
43. The thin plate is directly nailed to the wall and the sound absorption effect is very poor.
44, curtain fabric mainly absorbs high and medium frequency. î…•
45, the rough cement wall sound absorption effect is very poor.
46. ​​The human ear can determine the spatial orientation of the sound source through the intensity difference and time difference of the sound source signal, which is called the binaural effect.
47. Two sounds, one after the other, arrive at the human ear for 5ms--50ms, and the human ear feels that the sound is from the first arrival sound source, called the Haas effect.
48. The left and right sound sources have a sound intensity difference greater than 15 dB. The listener feels that the sound source is a sound source with a strong sound level, called the Deboe effect.
49. The listening threshold of a sound must be improved because of the existence of other sounds. This phenomenon is called the masking effect.
50. Due to the interference of sound in some places in the hall, some frequencies cancel each other out, and the sound pressure level is reduced a lot, called dead point.
51. The sound encounters a concave reflecting surface, causing the sound pressure level of a certain area to be much larger than other areas called sound focusing.
52. The sound is reflected back and forth between two parallel walls in the room to produce a plurality of identical sounds, called vibrating echoes.
53. Since the reflection makes the reflected sound and the direct sound differ by more than 50ms, an echo will occur.
54. The room is excited by external sound vibrations to vibrate according to its own natural frequency, called room resonance.
55. There are several overlapping phenomena with the same resonant frequency in the room, which is called the degeneracy of the resonant frequency.
56. The original sound signal spectrum is changed due to degeneracy and the like, and the added timbre is caused to cause distortion, which is called acoustic dyeing.
57. The distance between the point where the direct sound energy density in the sound field is equal to the density of the sound energy of the reverberation and the sound source is called the reverberation radius.
58. When the listening point is within the reverberation halfway, the direct sound plays a major role.
59. The listening sound plays a major role in reverberation when it is outside the reverberation halfway.
60. Sound source vibration causes the air to generate additional alternating pressure, called sound waves.
61. The vibration direction of the particle is perpendicular to the propagation direction of the wave, and is called a transverse wave.
62. The vibration direction of the particle is parallel to the propagation direction of the wave, which is called longitudinal wave.
63. The sound wave radiated by the general point sound source in space belongs to a spherical wave.
64. Sound waves travel in different materials, and the fastest is metal.
65. The slowest speed of sound waves in different materials is air.
66. Sound waves propagate in different materials, and their speed is metal > wood > water > air.
67. The echo is generated because the reflected sound is different from the direct sound by more than 50ms.
68. The tremor echo is generated because the sound is reflected back and forth between two parallel walls of light.
69. The sound focus is generated because the sound encounters a concave reflecting surface.
70. Sound diffusion occurs because the sound encounters a convex reflecting surface.
71. In a seat in the auditorium, the speech on the stage is changed into two repeated sounds. The possible reason is that the reflected sound is more than 50ms away from the direct sound.
72. The auditory characteristics of the human ear to different frequencies are most sensitive to the midrange, followed by the high pitch, and the lower the frequency, the less sensitive.
73. The directivity characteristics of sound waves of different frequencies are high directionality and low woofer directivity.
74. The diffracting ability of sound waves of different frequencies is easy to be diffracted by the bass, and the high sound is not easy to be diffracted.
75. The usual way of speaker layout is to hang the high-pitched speaker and adjust the angle; the woofer is close to the ground.殨~岪?76, the hall low frequency reverberation is too long,
A more effective measure is to load a thin plate with a cavity on the wall.
77. The best material for sound insulation is double-glazed brick wall with air layer in the middle.
78, 50HZ non-sinusoidal periodic signal, its 4th harmonic is 200HZ
79. The 3rd harmonic of the 100HZ non-sinusoidal periodic signal is 300HZ.
The 5th harmonic of the 80, 300HZ non-sinusoidal periodic signal is 1500HZ.
81, 80HZ non-sinusoidal periodic signal 5th harmonic is 400HZ.
82. To make the stadium unable to hear two sounds from the main speaker about 17m, a 50ms delay should be added to the sound box near the audience.
83. The equalizer divides the frequency band by 63, 125, 250, 500, 1K, 2K, 4K, 8K, and 16K, which is 1/1 octave division.
84. The equalizer divides the frequency band by 50, 200, 800, 3.2K, and 12K, and is divided by 4 times.
85. The equalizer divides the frequency band by 40, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400...20K, which is 1/3 octave division.
86. The best place to choose the best reverberation time is the concert hall.
87. The shortest place to choose the best reverberation time is the multi-track staging studio.
88. The suitable place to adjust the reverberation time is the multi-purpose hall.
89. The Sabin formula is applicable to the calculation of the reverberation time of a room with a small sound absorption coefficient.
90, Ai Run formula is suitable for calculating the reverberation time of various types of rooms.
91. The content of the Sabin formula is: the reverberation time is equal to 0.161X room volume / room surface area X sound absorption coefficient.
92. In order to reduce the degeneracy of the room and avoid sounding, the best length of the room: width: the height ratio is 2:3:5.
93. In the large theater, the seat that is most likely to hear the echo is the front seat.
94. The main way to solve the echoes heard by the audience in front of the large theater is to enhance the sound absorption on the back wall of the auditorium.
95, the correct way to write decibel is dB.
96. The 1 and i in the music notation are one octave apart.
97. The distance between 1 and 2 in the music notation is 1 degree.
98. Sound velocity C, acoustic wave frequency, acoustic wave wavelength λ, and the relationship between them is C=fxλ.
99. The relationship between the acoustic frequency and the acoustic period Τ is f=1/T.
100. The condition of standing wave formation is back propagation, the amplitude is the same, the frequency is equal, and the phase difference is 0 or constant.
101. CHORUS in the effect means chorus.
102. The local pressure of the medium caused by the disturbance of the sound wave changes, called sound pressure.
103. The unit of sound pressure level is dB.
104. The unit of the sound level is dB.
105. The unit of sound pressure is (Pa) Pa.
106. The unit of sound intensity is w/m2.
107. The sound pressure of the threshold is about 2×10-5Pa.
108. The sound pressure of the pain threshold is about 2×10 Pa.
109. The sound pressure level of the pain threshold is about 120 dB.
110. The sound pressure level of the threshold is about 0 dB.
111. The concave curved surface forms a concentrated reflection on the sound wave, so that the sound energy is concentrated at a certain point or a certain area, which is called sound focusing.
112. The convex curved surface reflects the sound wave, so that the sound energy forms a diffusion.
113. The minimum time interval between the human ear to distinguish the two sounds is 50 ms.
114. The melody in music includes vocal and instrumental melody.
115. In the music notation, 1-i is called octave.
116. Indoor reverberation is caused by reflected sound.
117. The basic tone is raised by a semitone and called the ascension, indicated by the # mark.
118. The basic sound is reduced by halftone and called down, which is indicated by the b mark.
119. The sound that has been raised or lowered has to become a basic sound called restoration, which is indicated by a ㄆ mark.
120, MIDI means the digital interface of the instrument.
121. The sound source generates a reflection between two parallel interfaces whose distance is greater than a certain value to form a series of echoes, called a vibrating echo.
122. The ratio of the sound pressure to the reference sound pressure (2×10-5Pa), and the logarithm of the base 10 is multiplied by 20, which is called the sound pressure level.
123. Most of the sounds in music are compound sounds.
124. Indoor early reflection sound refers to the reflection sound of the ear that has been reflected only once.
125. There are 7 basic sounds in music.
126. Two kinds of commonly used sound absorbing materials: porous materials, leaving a cavity after the thin plate.
127. Does not belong to sound insulation structure: perforated steel plate.
128. It belongs to sound insulation structure: double-layer brick wall.
129. Due to the change of the indoor frequency response, the original signal spectrum has been changed, which is called acoustic dyeing.
130, does not belong to the porous sound absorption material: gypsum board.
131. It belongs to porous sound absorbing material: rock wool.
132. Thin plate resonance structure The sound absorption feature is characterized by low frequency sound absorption and also contributes to the diffusion of sound waves.
133. Fixing the wooden board on the frame, leaving a certain air layer behind the board, can form a thin plate resonant sound absorbing structure.
134. The sound of the bird on the recording tree of the sound engineer is 0.01Pa, and the recording sound of the military number is 1Pa. The difference between the two sounds is 40dB.
135, reverberation can extend the duration of the sound, improve the fullness of the sound.
136. If the frequencies of the two sources are the same or similar, and the waves emitted are superimposed, wave interference may occur. î•
137. Two waves propagating in opposite directions on the same straight line. If the amplitude and frequency are the same, standing waves will appear on the connecting lines of the two wave sources.
138. The first level indicator of the total noise level of the language and music hall is NR30.
139. The first level indicator of the total noise level of the karaoke hall is 40dB [A].
140. The acoustic focusing generated indoors has an uneven influence on the indoor sound field, because the concave reflecting surface exists in the room.
141. There is a dead point in the indoor listening because the indoor sound source generates interference or forms a standing wave.
142. The sound shadow area refers to the area where the direct sound is not heard indoors.
143. The sound insulation R of the object is related to the thickness of the object and is related to its surface structure and density.
144. Laying enough sound absorbing material on the concave surface can solve the defect of sound focusing.
145. Adjusting the speaker position or adding a fill speaker can solve the defect of the sound shadow area.
146. Strong sound absorption or convex diffuser on the rear wall surface can solve the defect of long delay echo.
147. Adding a diffuser or changing the parallel angle on the surface of the parallel wall on both sides can solve the defect of the tremor echo.
148. A condenser microphone has a maximum sound pressure level of 126 dB, an equivalent noise level of 20 dB, and a dynamic range of 106 dB.
149. The mid-high frequency band of the audio determines the brightness and clarity of the sound.
150, the high frequency of the audio determines the color of the sound.
151. The low frequency band in the audio frequency determines the thickness and fullness of the sound.
152. The mid-low frequency band of the audio determines the sound strength.
153. The wave line refers to the direction of propagation of the wave.
154. The echo is caused by acoustic reflection.
155. When the indoor sound field is designed, the sound absorption performance of the sound absorption material on the wall of the room is stronger, and the smaller the amplitude of the early reflection sound, the shorter the reverberation time.
156. The object with smaller sound absorption coefficient α has a larger reflection sound. The object with a larger sound absorption coefficient has a smaller reflection sound.
157, the effect of early reflection sound is to give people a sense of intimacy.
158. After the interior decoration is completed, if the natural reverberation time T60 is long, the window door can be installed with a heavy fabric curtain to improve.
159. In the design of large halls, the near-reflex sound should be fully utilized.
160, the reverberation sound and the early reflection sounds match the sounds that make people feel fuller.
161. The sound pressure level and the sound intensity level are numerically the same.
162. Acoustic dyeing has an adverse effect on sound reinforcement.
163. The indoor sound frequency transmission characteristics are related to the sound absorption coefficient of surrounding objects.
164. The pitch is directly related to the sound frequency.
165. The room balance compensation curves of different rooms are different.
166. The sound intensity of the point source is inversely proportional to its distance.
167. The sampling frequency must be more than twice the highest frequency of the sampled signal.
168. The lower the frequency, the stronger the diffraction effect.
169. The unit of sound power is W.
170. The unit of sound pressure level is dB.
171. The unit of sound intensity is watts/square meter.
172. The unit of sound pressure is Pa (Pa).
173. The sound source and the listening person are in motion, and the listener will feel the frequency of the sound source changes. This phenomenon is called the Doppler effect.
174, the direct sound is delayed and inverted 180 degrees, superimposed on the direct sound, so that the human ear produces a spatial impression, called the Lloyd's effect.
175. People distinguish the subjective feelings of two different sounds having the same frequency and the same amplitude, called the timbre.
176. Among the three elements of sound, the elements mainly related to the frequency of sound are called tones.
177. The distance between the tones of two sounds is called the interval.
178. Arrange the sounds according to a certain interval, called a scale.
179. A signal whose instantaneous voltage changes sinusoidally with time is called a pure tone signal.
180. A series of pulse signals consisting of a certain number of sinusoidal waves, each of which has a certain requirement of discontinuity and duration, is called a click sound.
181, including various frequency components of 20 Hz to 20 kHz, and the energy distribution of each frequency is a uniform noise signal, called white noise.
182. A noise signal comprising various frequency components of 20 Hz to 20 kHz and having a power spectral density inversely proportional to the frequency is called pink noise.
183. Two microphones with directivity or non-directionality are collected at a distance between the ears of the human head, which is called A/B stereo system.
184. Two microphones are combined, one is a scalloped 8-shaped microphone, and the main body points to the left side; the other heart-shaped or non-directional microphone points to the front. The two microphone signals are connected to the matrix for "sum" and "difference" conversion and output, which is called M/S stereo system.
185. Two microphones whose directivity is a heart-shaped or 8-shaped shape are installed in the same microphone housing one above the other, and the angle between the main axes of the two changes within 0---360 degrees, which is called X/Y system. Stereo system.
186. The order in which the sound is heard at a certain point in the room to reach the human ear is direct sound, near-reflex sound, and reverb sound.
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