## Electroacoustical Reference DataThe need for a general collection of electroacoustical reference and design data in graphical form has been felt by acousticians and engineers for some time. This type of data can otherwise only be found in a collection of handbooks. Therefore, it is the author's intention that this book serve as a single source for many electroacoustical reference and system design requirements. In form, the volume closely resembles Frank Massa's Acoustic Design Charts, a handy book dating from 1942 that has long been out of print. The basic format of Massa's book has been followed here: For each entry, graphical data are presented on the right page, while text, examples, and refer ences appear on the left page. In this manner, the user can solve a given problem without thumbing from one page to the next. All graphs and charts have been scaled for ease in data entry and reading. The book is divided into the following sections: A. General Acoustical Relationships. This section covers the behavior of sound transmis sion in reverberant and free fields, sound absorption and diffraction, and directional characteris tics of basic sound radiators. B. Loudspeakers. Loudspeakers are discussed in terms of basic relationships regarding cone excursion, sensitivity, efficiency, and directivity index, power ratings, and architectural layout. c. Microphones. The topics in this section include microphone sensitivity and noise rating, analysis of directional properties, stereo microphone array characteristics, proximity effects, and boundary conditions. D. Signal Transmission. |

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### Contents

Sound Pressure and dB Lr Sound Pressure Level | 2 |

Frequency and Wavelength in Air | 4 |

Inverse Square Losses in a Free Field | 6 |

Attenuation with Distance from Plane and Line Sources in a Free Field | 8 |

Atmospheric Sound Absorption as a Function of Frequency and Relative Humidity I | 10 |

Atmospheric Sound Absorption as a Function of Frequency and Relative Humidity II | 12 |

Atmospheric Absorption Due to Inverse Square Losses and Relative Humidity | 14 |

NC and PNC Noise Criteria Curves | 16 |

HigherOrder Microphone Characteristics | 188 |

Microphone Line Losses | 190 |

SIGNAL TRANSMISSION | 193 |

Time Constant versus Frequency | 194 |

RIAA Disc Preemphasis and Deemphasis | 197 |

FM Broadcasting Preemphasis and Deemphasis | 198 |

Early 78 rpm and 33 rpm Disc Preemphasis and Deemphasis Standards | 201 |

Motion Picture Mono Optical Reproduce Standard | 202 |

Sound Transmission Class STC Curves | 18 |

Helmholtz Resonators | 20 |

Resonance Frequency for Pipes Open at Both Ends | 22 |

End Correction for Pipes | 24 |

Resonance Frequency for Pipes Open at One End | 26 |

Diffraction of Sound by a Cylinder a Cube and a Sphere | 28 |

Response Curves Showing Diffraction by 10 Objects of Different Shape | 30 |

Fresnel Diffraction over Sound Barriers | 32 |

Definition of Critical Distance | 34 |

Room Constant as a Function of Surface Area and Absorption | 36 |

Relation between 5 and In 15 in Reverberation Time Calculations | 38 |

Reverberant Level as a Function of Room Constant and Acoustical Power | 40 |

Mean Free Path MFP Room Volume and Surface Area | 42 |

Sound Attenuation over Distance in Semireverberant Spaces | 44 |

Critical Distance as a Function of Room Constant and Directivity Factor | 46 |

Acoustical Power Required to Produce a Level of 94 dB Lp as a Function of Room | 48 |

Volume and Reverberation Time | 49 |

Sound Pressure Level Produced by 1 Acoustic Watt as a Function of Room Constant and Distance from Source | 50 |

Estimation of Total Absorption When Room Volume and Reverberation Time Are Known | 52 |

Estimation of Room Constant When Room Volume and Reverberation Time Are Known | 54 |

Estimation of Room Boundary Area When Volume Is Known | 56 |

Reverberation Time Ratios with and without Atmospheric Losses | 59 |

Relationship between Directivity Factor and Directivity Index | 60 |

Wave number k as a Function of Piston Size and Frequency | 62 |

Polar Response of a Piston Mounted in a Large Baffle | 64 |

Polar Response of a Piston Mounted at the End of a Long Tube | 67 |

Polar Response of an Unbaffled Piston | 68 |

Offaxis Response of a Piston in a Large Baffle | 70 |

Directivity of a Piston in a Large Baffle at the End of a Long Tube and in Free Space | 71 |

LOUDSPEAKERS | 75 |

Transmission Coefficient versus Frequency for a Piston Mounted in a Large Baffle | 76 |

Normalized Mutual Coupling for Multiple Pistons | 78 |

Acoustical Power Output Produced on One Side of a Piston in a Large Baffle as a Function of Amplitude Radius and Frequency | 80 |

Sound Pressure Level Produced by a Piston in a Large Baffle at a Distance of 1 Meter as a Function of Amplitude Radius and Frequency | 82 |

Sound Pressure Level Produced by a Piston in a Large Baffle as a Function of Radiated Power and Distance | 84 |

Peak Amplitude for 1 Acoustical Watt Radiated by a Piston into HalfSpace as a Function of Radius and Frequency | 86 |

Transducer Cone Deflection as a Function of Resonance Frequency | 88 |

Second Harmonic Distortion in Horns | 90 |

Frequency Modulation FM Distortion in Cone Transducers | 92 |

Nominal Loudspeaker Efficiency as a Function of Onaxis Sensitivity and Directivity Index | 94 |

Sensitivity Ratings for Loudspeaker Systems | 96 |

Plane Wave Tube PWT Sensitivity Ratings for Compression Drivers | 98 |

Radiation Resistance for Various Horn Flare Development Curves | 100 |

HighFrequency Driver Electrical Derating for Flat Power Response Equalization | 102 |

Duty CycleRelated Power Ratings | 104 |

Resistance Change with Temperature for Copper | 106 |

Weighting Curves for Loudspeaker Power Measurements | 108 |

House Equalization Standard Curves for Sound Reinforcement and Program Monitoring | 110 |

Transducer Sensitivity as a Function of Atmospheric Pressure and Temperature | 112 |

Relation between 2n and 4n Loading and Baffle Size | 114 |

Horn Mouth Size versus 6 dB Beamwidth Control | 116 |

Beamwidth Control of Multicellular Horns | 118 |

Beamwidth Narrowing with Vertical Stacked Horn Arrays | 120 |

Directivity versus Horizontal and Vertical Beamwidth | 122 |

Beamwidth and Directivity Characteristics of a Pair of 250mrn 10in LowFrequency Transducers | 124 |

Beamwidth and Directivity Characteristics of a Pair of 300mm 12in LowFrequency Transducers | 126 |

Hexagonal Array | 130 |

Square Array | 132 |

Dividing Networks 6 dB per Octave Slopes | 134 |

Dividing Networks 12 dB per Octave Slopes | 136 |

Porting Data for Vented Loudspeaker Enclosures | 138 |

ThieleSmall Parameters for LowFrequency Horn Applications | 140 |

Simple Line Arrays | 142 |

MICROPHONES | 145 |

Nomograph for Microphone Output Power and Voltage versus Microphone Impedance | 146 |

Microphone SelfNoise Rating Curves | 148 |

El A GM Microphone Sensitivity Rating | 150 |

FirstOrder Microphone Pattern Data | 152 |

MidSideXY Conversion Data | 154 |

Random Energy Efficiency Directivity Factor and Distance Factor as a Function of Polar Pattern | 156 |

FronttoTotal Ratio as a Function of Polar Pattern | 158 |

FrontBack Ratio versus Polar Pattern | 160 |

Omni and Bidirectional Components of the FirstOrder Cardioid Family | 162 |

BacktoBack Cardioid Components of the Firstorder Cardioid Family 164 | 166 |

MidSide MS and XY Microphone Pairs | 168 |

Multipath and Muldmicrophone Interference Effects | 170 |

Effect of Dipole Dimension on Directional Microphone Frequency Response | 172 |

Basic Proximity Effect in Directional Microphones | 174 |

Proximity Effect in a Dipole Microphone at Several Distances | 177 |

Onaxis Proximity Effect in a Cardioid Microphone at Several Distances | 178 |

Proximity Effect in a Cardioid Microphone as a Function of Azimuth Angle | 180 |

Onaxis and Diffuse Field Incidence Response of Omnidirectional Microphones | 182 |

Delay versus Level for Accent Microphones in Recording | 184 |

Microphone Boundary Size versus 27t to 4lt Transition Frequency | 186 |

Digital Preemphasis and Deemphasis Standard | 204 |

Comparison of Meters Used in Broadcasting and Recording | 206 |

Power Ratios Expressed in dBm | 208 |

Voltage Ratios Expressed in dBu | 210 |

Power Ratios Expressed in dBW | 212 |

Voltage Ratios Expressed in dBV | 214 |

Sine Wave Voltage Output versus DC Voltage Capability | 216 |

Resistance Values for Various Lengths and Gauges of Copper Wire | 218 |

Metric Wire Gauges | 221 |

HighFrequency Transducer Protection Capacitors | 222 |

Design of Symmetrical Tpads | 224 |

Design of Lpads | 226 |

Summing of Levels | 228 |

Distortion Percentage and Level | 230 |

Load Impedance as a Function of Power Input in 70volt 100volt and 25volt Distribution Systems | 232 |

Maximum Wire Runs for 0 5dB Loss in 70volt Systems | 234 |

Peak and rms Values of Waveforms | 236 |

Input and Output Impedances of Electronic Devices | 238 |

Loudspeaker Damping Factor as a Function of Line Length and Wire Gauge | 242 |

Direct Field Considerations | 244 |

Reverberant Field Considerations | 246 |

One Channel to Two | 248 |

One Channel to Three | 250 |

One Channel to Four | 252 |

Effect of Noise on Speech Communication | 254 |

Equivalent Acoustic Distance EAD and AWeighted Noise Level | 256 |

Hor n Coverage Angle as Seen in Plan View | 258 |

Peutzs Percentage Articulation Loss of Consonants AlIOJ | 260 |

Augspurgers Modification of Peutzs Data | 262 |

Calculation of Articulation Index AI | 264 |

Typical Motion Picture Screen Losses | 266 |

House Equalization Standard for Motion Picture Systems | 268 |

Adjustments for House Size | 270 |

ISO Preferred Numbers | 272 |

PSYCHOACOUSTICAL DATA | 275 |

FletcherMunson Equal Loudness Contours | 276 |

RobinsonDadson Equal Loudness Contours | 278 |

ChurcherKing Equal Loudness Contours | 280 |

Determination of Twice Loudness at Low Frequencies | 282 |

Calculation of Loudness in Sones | 284 |

Standard Weighting Curves | 286 |

Loudness and Signal Duration | 288 |

Pitch and Level Relationships I | 290 |

Pitch and Level Relationships II | 292 |

Frequency and Pitch Relationships | 294 |

Critical Bandwidth | 296 |

Annoyance Due to Echo Effects | 298 |

Blauert and Laws Criterion for the Audibility of Signal Group Delay | 300 |

Optimum Reverberation Time as a Function of Room Volume and Usage | 302 |

Optimum Reverberation Time as a Function of Frequency | 304 |

Subjective Effects of First Reflections in a Concert Hall | 306 |

Binaural Lateral Masking | 308 |

Franssens Data | 310 |

The Precedence Effect Haas Effect | 312 |

Bauers Stereophonic Law of Sines | 314 |

Pressures and Pressure Levels Generated by a Variety of Sound Sources | 316 |

Typical Male Speech Spectra | 318 |

Hearing Threshold Shift as a Function of Age | 320 |

MUSICAL INSTRUMENTS | 323 |

Frequency Ranges of Musical Instruments and the Human Voice | 324 |

Dynamic Ranges of Wind and String Instruments | 326 |

Directional Properties of Brass Instruments | 328 |

Directional Properties of Woodwind Instruments | 330 |

Directional Properties of String Instruments | 332 |

Octave Band Spectral Amplitude Distribution Music Sources | 334 |

ANALOG MAGNETIC RECORDING | 339 |

Track Width Standards for Professional Magnetic Recording | 340 |

Track Width Standards for Consumer Tape Formats | 343 |

Azimuth Losses in Tape Playback | 344 |

Oxide Thickness Losses in Tape Playback | 346 |

Spacing Losses in Tape Playback | 348 |

Gap Length Losses in Tape Playback | 350 |

Reference Surface Flurivity Standards for Tape Recording | 352 |

IEC Equalization Standards for Professional Tape Playback | 355 |

NAB National Association of Broadcasters Standard for Professional Tape Playback | 356 |

AES Audio Engineering Society Standard for Professional Tape Playback at 76 cmsec 30 insec | 358 |

Standards for Playback of Consumer Tape Formats | 360 |

IEC to NAB Conversion at 38 cmsec | 363 |

IEC to NAB Conversion at 19 cmsec 364 | 366 |

Unit Conversion Table | 368 |

369 | |

375 | |

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### Common terms and phrases

2k Frequency Hz A-weighted abscissa and move abscissa and read absorption accent microphones acoustical power acoustical watts approximately array attenuation beamwidth Beranek bold line marked calculated cardioid cm/sec corresponding coverage angle crest factor cutoff frequency dB Lp Decibels diameter dipole directivity factor directivity index distortion doubling of distance driver Eargle EXAMPLE first-order following equation given graph high-frequency horn Large Baffle length listener load locate the value loss loudspeaker low-frequency measured move upward msec noise level nominal nomograph normally octave octave band ohms on-axis ordinate and read output voltage panpot pattern peak pipe plane proximity effect quadraphonic radiation range ratio read the value read upward recording References resonance frequency reverberant level reverberation RIAA room constant room volume sensitivity shown in Figure signal sound pressure level SOUND TRANSMISSION CLASS space speech square meters standard stereophonic Tape Playback tone transducer voltage wavelength weighting curve wire