# Workbook 8: Noise and Vibration > **Note:** Please DO NOT WRITE in workbooks. Answer on separate piece of paper. --- ## Table of Contents | Section | Page | |---------|------| | Instructions for Remainder of Workbook | 9 | | Introduction | 10 | | Noise | 11 | | Sound Waves and Hertz | 11 | | Airblast and Vibration Travel | 14 | | Distance Formula | 16 | | Seismographs | 17 | | Summary | 18 | | Test | 19 | --- ## Section 1: Basic Concepts **1.** Noise and vibration are (CHECK THE CORRECT ANSWER): - A. serious consideration in the blasting operations of the entire mining industry. - B. irritants, but they don't cause damage. - C. problems which the general public must learn to live with. **2.** Noise is defined as (all/unpleasant - which?) _____________ sounds? **3.** Two categories of sound are: - A. those which maintain (or build to) a level and hold it - _____________ sounds. - B. those which are sudden and might be startling - _____________ sounds. **4.** The intensity of sound is measured in _____________. **5.** Blasting produces mostly (high/low - which?) _____________ frequency sounds. **6.** Most instruments used to monitor or measure blasting sounds are based on (CHECK THE CORRECT ANSWER): - A. A-weighted scales, to measure high-frequency sounds. - B. B-weighted scales, to measure mid-frequency sounds. - C. C-weighted scales, to measure low-frequency sounds. --- ### Answers - Section 1 1. A is correct. 2. unpleasant 3. A. steady state, B. dynamic 4. decibels (dB's) 5. low 6. C is correct. --- ## Section 2: Airblast Basics **1.** The compressional wave in the air resulting from a shot is called _____________. **2.** There are two parts to an airblast: - A. that with a frequency of 20 Hertz and under, known as the _____________ element, which (can/cannot - which?) _____________ be heard. - B. that with a frequency of 20-20,000 Hz, which is a _____________ wave that (can/cannot - which?) _____________ be heard. **3.** The part of airblast which can cause the greatest structural damage to buildings is the (sound/concussion - which?) _____________ wave. **4.** Concerning the air in relation to airblast, two key factors are _____________ and _____________. **5.** Sound waves travel faster in (warm/cold - which?) _____________ air. **6.** Sound waves (CHECK THE CORRECT ANSWER): - A. always travel in a straight line. - B. will bend toward their faster-moving element, which will be in cold air. - C. will bend toward their slower-moving element, which will be cold air. **7.** In a temperature inversion, cold air will be located (close to/well above - which?) _____________ the ground, with warm air located (above/below - which?) _____________ the cold air. **8.** "Focusing" can occur when a _____________ exists and the _____________ direction is pronounced, with sound increasing when faster- and slower-moving sound waves combine, which can occur (only near/perhaps miles from - which?) _____________ the site of the blast. --- ### Answers - Section 2 1. airblast 2. A. concussion, cannot; B. sound, can 3. concussion 4. temperature, wind (IN EITHER ORDER) 5. warm 6. C is correct. 7. close to, above 8. temperature inversion, wind, perhaps miles from --- ## Section 3: Controlling Airblast **1.** While you can't always wait for ideal shooting conditions, you can take certain steps in regard to your shooting schedule to help control airblast. These include the following (CHECK ANY CORRECT ANSWERS): - A. avoid shooting during temperature inversions. - B. shoot in the morning, whenever possible. - C. shoot on foggy, hazy days, since sound travels slower in such conditions. - D. avoid shooting when it's especially windy. - E. if possible, don't shoot when the temperature is dropping rapidly. **2.** Such lines as _____________ cord and blasting _____________ should be covered with _____________ to help control airblast. **3.** The use of adequate _____________ above the explosives in a hole can be helpful. **4.** To be sure shots detonate as planned, thereby minimizing airblast effects, use _____________ properly. **5.** Proper _____________ and _____________ can help prevent blowouts, resulting in better control of airblast and flyrock. --- ### Answers - Section 3 1. A, D, and E are correct. 2. detonating (cord), caps, dirt 3. stemming 4. delays 5. burden, spacing (IN EITHER ORDER) --- ## Section 4: Ground Vibration **1.** Simply stated, vibration is _____________. **2.** The three aspects of ground vibrations that determine how people react to them are _____________, _____________, and _____________ of the vibration. **3.** Vibrations caused by blasting are usually (steady state/dynamic - which?) _____________, so people tend to react more to them. **4.** A truck passing by or a jet plane taking off can cause greater vibrations than those resulting from a blast. - A. True. - B. False. **5.** In the following list, check any steps that can help control ground vibrations due to blasting operations. - A. Allow extra burden and spacing. - B. Vary from the blasting plan whenever it seems appropriate. - C. Use the proper charge weight per delay. - D. Provide maximum relief to the burden. --- ### Answers - Section 4 1. movement 2. duration, amplitude, frequency (IN ANY ORDER) 3. dynamic 4. A is correct. 5. C and D are correct. --- ## Instructions for Remainder of Workbook The remainder of this workbook is presented in programmed instruction as described in the Instructions to the program. This will help you learn faster - and remember the material longer. --- ## Introduction The problems we're concerned with here are related to those areas where operators must conduct blasting operations in close proximity to populated areas. We do not intend, in any way, to minimize our concern for the safety and well-being of mine employees. The purpose of this discussion is to make you aware of the necessity of applicable regulations and Company policies which are primarily directed toward what occurs outside the permit area during blasting. Thoughts presented here will help protect the public, but also protect you, your job, and your Company. --- ## Noise **1.** You know from the tape/slide segment that, for our purpose, noise is defined as _____________ sounds, and vibration is _____________. **2.** If you combine excessive noise and vibration with blasting, the results could be unfortunate for the construction company as well as the general populace near the mine. These elements of the blasting operation are (CHECK THE CORRECT ANSWER): - A. of little concern to the mining industry. - B. extremely important to a company's involvement in blasting. - C. uncontrollable and must be ignored. **3.** Early in the program, we talked about the human response to noise or unpleasant sounds. And, you remember that noise level is measured in (particle velocity/decibels - which?) _____________. **4.** This human response to the noise produced by a blast is one of the major concerns facing mining operations. Airblast or concussion produced by blasting (may/will not - which?) _____________ cause many complaints from mine neighbours. **5.** We know that people are disturbed or distressed by noise (CHECK THE CORRECT ANSWER): - A. at about the point at which some damage might occur. - B. well below the damage level. - C. after the noise level has gone above the level where some windows will crack. **6.** But, the point is, the mining industry wants very much to be able to continue with the procedures necessary for completion of their operations without disturbing the general public unnecessarily. Accurate job performance (will/will not - which?) _____________ help control excessive vibration. --- ## Sound Waves and Hertz **7.** We've talked briefly about noise levels as related to airblasts, so now, let's go one step further. When we say sound waves, we mean waves much like those which occur when you throw a pebble into water. This illustration shows one complete cycle of a sound wave. It leaves the "0" line, reaches its peak value, crosses "0" again to its low point, and then returns to zero. Therefore, one complete "event" of this type, beginning and ending at zero, corresponds to one complete _____________. **8.** These cycles can be counted. The number of cycles completed per second determines the frequency of the sound. The more cycles per second the higher the frequency. Decrease the cycles and low frequency sounds are produced. For example, the scream of a jet plane is (high/low - which?) _____________ frequency, and the rumble of thunder is (high/low - which?) _____________ frequency. **9.** We said that the cycles per second can be counted. These units - or the number of cycles per seconds - are called hertz, abbreviated Hz. Low frequency sounds imply lower numbers of hertz; therefore (CHECK THE CORRECT ANSWER): - A. high frequency sounds imply large hertz numbers. - B. high and low frequency sounds are measured in the same number of hertz. - C. high frequency sounds are very difficult to relate to hertz. **10.** The lower frequency wave is depicted by Example (1/2 - which?) _____________ and the higher frequency wave is Example _____________. **11.** Look at the illustration once again. Now, determine the frequency of each wave. Remember, a complete cycle involves leaving, crossing, then re-attaining the zero line. - A. Example 1 = _____________ Hz. - B. Example 2 = _____________ Hz. **12.** All of this leads up to this point: The human ear picks up sounds from 20 hertz to 20,000 hertz. So, sound waves below 20 hertz or above 20,000 are (audible/inaudible - which?) _____________. **13.** We've talked quite a bit about decibels and hertz, now. From what you have studied, you could logically assume that decibels refer to the (loudness/pitch - which?) _____________ of the sound waves, and frequency denotes the (loudness/pitch - which?) _____________. **14.** All of these facts tie in with our study of airblasts. Airblasts produce sound waves which are measured in _____________. **15.** You know that airblasts produce noise which is heard. So, the number of cycles per second, or _____________, must be in the (20-20,000/50-50,000 - which?) _____________ range. **16.** Sound waves which are inaudible to the human ear can sometimes be felt. A concussion from an airblast produced by blasting measures less than 20 hertz, so it is (CHECK THE CORRECT ANSWER): - A. both heard and felt. - B. felt, not heard. - C. neither felt nor heard. **17.** Therefore, an airblast produces two distinct effects: - A. the _____________ or sound which you hear; and, - B. the _____________, which you (hear/feel - which?) _____________. **18.** Perhaps we should mention some common causes of airblasts - first, the energy release by unconfined explosives. To avoid this type of airblast, simply avoid the use of _____________ explosives. **19.** The release of high-pressure gases cause airblast. This occurs when the force of the explosion forces the trapped gases up and out the hole (a "blowout"). These entrapped gases are held underground, under pressure. Upon release from their pressurized confinement, they will (CHECK THE CORRECT ANSWER): - A. leak away into cracks in the ground and quickly dissipate. - B. be immediately burned up by the explosion. - C. erupt from the borehole with such force that an airblast will develop. **20.** With proper patterns, stemming, etc., this type of airblast (can/cannot - which?) _____________ be prevented, controlled, or minimized. **21.** In summary: - A. The pattern of the wave, from the zero line to its high point, then to the maximum point below the line, and finally back to the line again, illustrates one complete _____________. - B. A sound with a relatively small number of cycles per second is a _____________ sound, and a sound with a greater number of cycles per second is a _____________ sound. - C. The units, or cycles per second, are called _____________. - D. The human ear detects sounds from _____________ up to _____________ hertz. - E. Airblasts produce waves which are both _____________ and _____________. - F. Airblast is measured in _____________. - G. Concussion cannot be _____________, but is _____________. - H. Two causes of airblasts are unconfined _____________ and _____________. --- ## Airblast and Vibration Travel **22.** Let's take the time to expand a little on the manner in which airblasts and vibration travel. An airblast normally travels like this: Under normal atmospheric conditions, the sound waves move with (equal/great variations in - which?) _____________ intensity in all directions from the sound source. **23.** But when a temperature inversion exists, atmospheric conditions have forced (CHECK THE CORRECT ANSWER): - A. warm air even closer to the ground. - B. the cold air down to the surface and the warm air above it. - C. an equal mixture of cold and warm air, with no division between the two. **24.** When a temperature inversion exists, sound waves travel in this manner: ``` WARM AIR --------- COLD AIR --------- GROUND ``` This means they will travel faster in the (warm/cold - which?) _____________ air, but will bend toward the slower-moving element which, in this case, is (away from/close to - which?) _____________ the ground. **25.** Under normal conditions, more of the sound waves will travel up and over dwellings and structures, since they'll bend toward the colder air located well above the surface. But with temperature inversion, they (will/will not - which?) _____________ be bent and come back closer to the ground. **26.** So, in regard to the sound waves produced by blasting, weather conditions (CHECK THE CORRECT ANSWER): - A. need not be a consideration. - B. have a great influence on the travel through the air, and even the force or power of, the waves. - C. usually help diminish the force. **27.** In addition to airblast, an explosion causes waves to move through the earth. These are called seismic waves. Such waves, or vibrations, can be insignificant, harmless ripples, or they may be very strong, perhaps even causing damage. In general, however, it's safe to say that the vibrations caused by blasting are probably (CHECK THE CORRECT ANSWER): - A. more disturbing than damaging. - B. damaging to structures in every case, since dynamic sounds such as these shake structures severely. - C. never damaging, even though they're always disturbing to people. **28.** Since airblast is generally the cause of bad community relations, let's talk about some of the most common causes of airblast. When a hole is overloaded, in comparison to the amount of burden to be broken, the result will be greater airblast and flyrock. This is true because the heavy explosive loading will (CHECK THE CORRECT ANSWER): - A. easily shatter the rock burden and throw rock and high temperature gases into the air. - B. not break the overbreak but will produce airblast. **29.** Properly developed blasting patterns will help reduce both airblast and vibrations and also produce the desired breakage. So proper stemming, loading, etc., will help to: - A. (increase/decrease - which?) _____________ safety and promote production efficiency; and, - B. reduce airblast and flyrock which will greatly enhance the safety factor, and probably (increase/decrease - which?) _____________ complaints from the neighbours. --- ## Distance Formula **30.** The vibration produced by every shot is an important element of all blasting. In fact, careful monitoring and a close control of vibrations can mean the difference between continued operation and a mine closure. There are a couple of methods used to assure the control of vibrations. First, there's an equation used to determine the maximum weight of _____________ which can be detonated within any 8-millisecond time span - the amount of time that must exist between delays for each blast to be considered a separate _____________. **31.** The formula used to determine allowable weight of explosives per 8-millisecond period is: **W = (D/60)²**. In this equation, "W" equals the maximum weight of explosives, in pounds; and "D" equals the distance, in feet, to the nearest dwelling, church, school, or commercial or institutional building. Before you can calculate "W", you must know (CHECK THE CORRECT ANSWER): - A. how many pounds of explosives can be loaded into each hole. - B. how deep the boreholes are to be drilled. - C. the distance, in feet, to the nearest structure of concern. **32.** Okay, let's see how this formula works. Let's assume a distance, or "D", of 360 feet to the nearest dwelling. Now, our equation looks like this: **W = (360/60)²** First, divide 360 by 60, to get: W = (6)² = 6 × 6 = **36 pounds of explosives**. **33.** Now, using the formula W = (D/60)², determine the maximum weight in pounds of explosives which can be detonated in 8-millisecond periods when the distances involved are: - A. 420 feet. W = _____________ - B. 600 feet. W = _____________ - C. 1200 feet. W = _____________ - D. 5400 feet. W = _____________ **34.** The pounds of explosives used per 8 milliseconds (increases/decreases - which?) _____________ rapidly as the distance between blast and buildings decrease. **35.** This equation is easy to calculate, but there are some charts available with the calculations already made: | Distance, in feet (D) | Maximum Weight, in pounds (W) | |----------------------:|------------------------------:| | 350 | 34 | | 400 | 44 | | 500 | 69 | | 600 | 100 | | 700 | 138 | | 800 | 178 | | 900 | 225 | | 1,000 | 278 | | 1,100 | 336 | | 1,200 | 400 | | 1,300 | 469 | | 1,400 | 544 | | 1,500 | 625 | | 1,600 | 711 | | 1,700 | 803 | | 1,800 | 900 | | 1,900 | 1,002 | | 2,000 | 1,111 | | 2,500 | 1,736 | | 3,000 | 2,500 | | 3,500 | 3,402 | | 4,000 | 4,444 | | 4,500 | 5,625 | | 5,000 | 6,944 | However, it is important that you understand how these amounts were determined. And, if holes are loaded according to these figures, the vibrations produced by the blasts (should/should not - which?) _____________ cause damage to buildings. --- ## Seismograph **36.** One device is quite useful in measuring various aspects of blasts. This is the same kind of instrument that's used to measure earthquakes, and it's called a _____________. **37.** A seismograph records three traces: horizontal, or back and forth; vertical or up and down; and, transverse, or left and right movement. When a seismograph is used to monitor vibration, these three traces are recorded (CHECK THE CORRECT ANSWER): - A. automatically. - B. by the foreman. - C. only when the particle velocity exceeds the legal limit. **38.** The seismograph enables you to determine, through a series of calculations, the particle velocity, because it records the (CHECK THE CORRECT ANSWER): - A. horizontal particle movement only. - B. movement of the particles of the ground in all directions. - C. atmospheric conditions which affect blasting. **39.** Many companies lease seismographs and place them around the perimeter of the permit area. Sometimes these devices are placed inside buildings owned by the company or private citizens. Then, at specified times, like once a week, the tapes are removed from the devices and sent to the leasing company for analysis. The analysis will provide an indication as to how much _____________ is being produced by the blasting operation. --- ## Summary **40.** As you are probably well aware, blasting is a very controversial matter. All companies are becoming more concerned with the public relations aspect. A failure to communicate with the surrounding community can make it difficult to run a successful operation. Public opinion (can/cannot - which?) _____________ have a direct bearing on blasting. **41.** One way to secure the company's position in the community and to greatly reduce complaints is for everyone involved to do his or her job in the most accurate, efficient manner possible. This mode-of-operation works for the betterment of all parties - not only the general public, but also will insure safer working conditions and increased production. --- You have now completed this workbook on Noise and Vibration. The information you've studied here will be helpful on the job as well as in upcoming workbooks. --- ## Test: Noise and Vibration **1.** Decibels indicate the degree of: - A. Sound intensity. - B. Vibrations. - C. Sound waves. - D. Discomfort to people within hearing distance. **2.** The noise from blasting is primarily: - A. Low-frequency. - B. High-frequency. - C. Of a weighted frequency. - D. None of the above. **3.** Instruments using C-weighted scales to monitor blasting sounds are measuring: - A. High-frequency sounds only. - B. Mid-frequency sounds only. - C. Low-frequency sounds only. - D. All sound frequencies. **4.** The frequency sounds that are the least damaging to hearing are: - A. Weighted frequency sounds. - B. Low-frequency sounds. - C. High-frequency sounds. - D. Sounds of about mid-frequency range. **5.** When a concussion from a blowout is felt inside a structure, the structure is actually: - A. Moved. - B. Damaged extensively. - C. Not affected at all. - D. Destroyed. **6.** Temperature inversion occurs when atmospheric conditions: - A. Force the warm air down and the cold air up. - B. Mix the air currents so they are neither warm nor cold. - C. Force the warm air up and the cold air down. - D. Result in fog. **7.** A simple definition of vibration is: - A. Concussion. - B. Velocity. - C. Movement. - D. Noise. **8.** Sound waves produced by blasting operations, travelling through the air can produce: - A. Noise and airblast. - B. Body waves and surface waves. - C. Both A and B are correct. - D. None of the above are correct. **9.** The movement of vibration is called: - A. Particle velocity. - B. Vibration velocity. - C. Ground velocity. - D. Steady state velocity. **10.** The concussion element of an airblast can be: - A. Felt only. - B. Heard only. - C. Both felt and heard. - D. Never felt nor heard. **11.** Noise usually becomes disturbing to people: - A. At about the point structural damage could occur. - B. Before any physical or structural damage can occur. - C. At about the point physical damage can occur. - D. Well after the point of structural damage. **12.** A natural cause of airblast is when pressurized gases from underground: - A. Erupt forcefully from the borehole. - B. Leak into cracks in the ground around a blasting area. - C. Are burned up during a blast. - D. All of the above are correct. **13.** Weather conditions: - A. Are a definite consideration when blasting. - B. Are only an important consideration in case of electrical storms during blasting. - C. Never affect blasting. - D. Have a small but unimportant effect on a successful blast. **14.** Some methods of controlling vibration include: - A. Layouts of the blast pattern. - B. Reduced charge weight per delay. - C. Both A and B are correct. - D. None of the above. **15.** The most favourable weather conditions for blasting are: - A. Clear skies with warm temperatures. - B. Hazy or foggy days. - C. Clear skies with cold temperatures. - D. Rainy days. **16.** Noise is defined as an unpleasant: - A. Sound. - B. Movement. - C. Vibration. - D. Decibel. **17.** One complete vibration, from the high point to the low point of a sound wave, is called a: - A. Decibel. - B. Cycle. - C. Hertz. - D. All of the above. **18.** Maximum relief provided to the burden helps: - A. Increase shot noise. - B. Reduce blowouts and vibration. - C. Provide greater safety during the shot. - D. Make vibrations more noticeable. **19.** The human ear picks up sounds ranging in frequency from: - A. 0-20,000 hertz. - B. 20-30,000 hertz. - C. 20-20,000 hertz. - D. 30-35,000 hertz. **20.** The pitch of sound waves is a result of their: - A. Loudness. - B. Frequency. - C. Decibels. - D. Velocity. **21.** An airblast concussion produced by blasting measures less than 20 hertz, so it is: - A. Both heard and felt. - B. Neither felt nor heard. - C. Heard, but not felt. - D. Felt, but not actually heard. **22.** A common cause of airblast is: - A. Confined explosives. - B. Unconfined explosives. - C. Both A and B are correct. - D. None of the above are correct. **23.** "Normal atmospheric conditions" means that the: - A. Cold air lies along the ground surface, with warmer air above it. - B. Warm air lies along the surface of the ground, with colder air above it. - C. Temperature of the air both along the ground surface and above it are almost the same. - D. None of the above. **24.** During a temperature inversion, sound waves travel: - A. Down into the surface of the ground. - B. Away from the ground's surface. - C. Straight up from the ground's surface. - D. Close to the surface of the ground. **25.** An increase in the effects of an airblast due to temperature inversion is called: - A. Censoring. - B. Vibrational increase. - C. Focusing. - D. Delineation. **26.** A seismograph determines particle velocity by recording: - A. Horizontal particle movement. - B. Atmospheric conditions which affect blasting. - C. Movement of the particles of the ground in all directions. - D. All of the above. **27.** The formula used to determine allowable weight of explosives per 8-millisecond period is: - A. Distance = (Weight/60)² - B. Weight = (6/Distance)² - C. Depth = (Weight/60)² - D. Weight = (Distance/60)² **28.** One device that is quite useful in measuring various aspects of blasts is the: - A. Sensorgraph. - B. Sonargraph. - C. Seismograph. - D. Blasting galvanometer. **29.** Sound waves: - A. Travel at random. - B. Always travel in a straight line. - C. Will bend toward slow-moving cold air. - D. Will bend toward faster-moving warm air. **30.** The Provincial government regulates the particle velocity of all blasts: - A. To some degree. - B. Not at all. - C. Very closely. - D. Only when so requested by area residents. --- ## Answer Key ### Test Answers | Question | Answer | |:--------:|:------:| | 1 | A | | 2 | A | | 3 | C | | 4 | D | | 5 | A | | 6 | C | | 7 | C | | 8 | A | | 9 | A | | 10 | A | | 11 | B | | 12 | A | | 13 | A | | 14 | C | | 15 | A | | 16 | A | | 17 | B | | 18 | B | | 19 | C | | 20 | B | | 21 | D | | 22 | B | | 23 | B | | 24 | D | | 25 | C | | 26 | C | | 27 | D | | 28 | C | | 29 | C | | 30 | C | ### Fill-in-the-Blank Answers (Programmed Instruction) **Noise Section:** - 1: unpleasant, movement - 2: B (extremely important) - 3: decibels - 4: may - 5: B (well below the damage level) - 6: will **Sound Waves and Hertz:** - 7: cycle - 8: high, low - 9: A (high frequency implies large hertz numbers) - 10: 1, 2 - 12: inaudible - 13: loudness, pitch - 14: decibels - 15: hertz, 20-20,000 - 16: B (felt, not heard) - 17: noise, concussion, feel - 18: unconfined - 19: C (erupt from borehole) - 20: can - 21: A. cycle; B. low, high; C. hertz; D. 20, 20,000; E. concussion, sound (or noise); F. decibels; G. heard, felt; H. explosives, blowouts **Airblast and Vibration Travel:** - 22: equal - 23: B (cold air to surface, warm air above) - 24: warm, close to - 25: will - 26: B (great influence) - 27: A (more disturbing than damaging) - 28: A (shatter rock burden) - 29: A. increase; B. decrease **Distance Formula:** - 30: explosives, delay - 31: C (distance to nearest structure) - 33: A. 49 lbs; B. 100 lbs; C. 400 lbs; D. 8,100 lbs - 34: decreases - 35: should not **Seismograph:** - 36: seismograph - 37: A (automatically) - 38: B (movement in all directions) - 39: vibration **Summary:** - 40: can --- *This workbook is the property of Maritime Blasting Services Ltd., Moncton, NB*