Sound Reproduction

Floyd E. Toole is a consultant for Harman and a Fellow of the AES, the Acoustical Society of America and CEDIA, and is in the Consumer Technology Hall of Fame.

Acknowledgements

Introduction

Chapter 1: Sound Production vs. Sound Reproduction








Live Classical Musical Performances



Live Popular Music Performances



Reproduced Sound – The Audio Industry



Preserving the Art – The Circle of Confusion



Music and Movies – the State of Affairs



The Role of Loudspeakers and Rooms



Human Adaptation, a Reality the Cannot be Ignored



Human Suggestibility



Chapter 2: A Scientific Perspective on Audio








Requirements for Scientific Investigations



Chapter 3: Subjective Measurements – Turning Opinion into Fact








Is Blind Listening Necessary?



Hearing Ability and Listener Performance



Stress and Strain



How Many Channels?



Controlling the Variables in Subjective Evaluations





Controlling the Physical Variables





The Listening Room – Making Tests Blind



Real-time Loudspeaker Comparison Methods



Binaural Record/Replay Loudspeaker Comparisons



Listener Position and Seating



Relative Loudness



Absolute Loudness – Playback Sound Levels



Choosing Program Material



Power Amplifiers, Wire and So Forth




Controlling the Psychological Variables



How to do the Test





Is it preference or accuracy that is evaluated?








Chapter 4: The Perceptual and Physical Dimensions of Sound





The Frequency Domain



The Amplitude Domain



Amplitude and Frequency Together: Frequency Response



Amplitude and Frequency Together: Equal-Loudness Contours





Loudness Controls and Tone Controls – Do They Work, Are They necessary?




The Boundaries of What We Can Hear





What Is Acceptable Background Noise?




Linear Distortions: Amplitute and Phase vs. Frequency





Spectral Tilt



Resonances Viewed in Frequency and Time



Finding and Fixing Resonances



A Persistent Problem: Differentiating Between Evidence of Resonances and Acoustical Interference



Critical bands, ERBNs, and the "resolution" of the hearing system




Amplitude, Frequency and Time Together: Waterfall Diagrams



Phase and Polarity – Do We Hear Waveforms?





The Audibility of Phase Shift and Group Delay



Phase Shift at Low Frequencies: a Special Case



The Audibility of Absolute Polarity




Non-Linear Distortions



Wavelength, the Key to Understanding Much in Audio





Loudspeaker Directivity



Room Resonance Basics



Resistive/Porous Absorbers and Membrane/Diaphragmatic Absorbers



Diffusers and Other Sound Scattering Devices





Chapter 5: Characterizing Loudspeakers – Can We Describe What is Good?








The Wisdom of the Ancients



Identifying the Important Variables – What do we Measure?



Anechoic Measurements – the Spinorama Evolves



Total Sound Power as a Measured Parameter



Why do we measure what we do? Are there better ways?



Predicting Room curves From Anechoic Data – An Exercise in curve Matching.





A Message About Sound Absorption and Scattering



Why Do We Care About Room Curves?




Closing the Loop − Predicting Listener Preferences From Measurements





The Olive Experiments – Part One



The Olive Experiments – Part Two



The Olive Experiments – Part Three




Loudspeaker Resonances – Detection and Remedies



Summary and Discussion



Chapter 6: Loudspeaker/Room Systems – an Introduction








One Room, Two Sound Fields – The Transition Frequency



A Brief History of Loudspeaker/Room Interactions



Timbral and Spatial Effects Attributable to Rooms



Chapter 7: Above the Transition Frequency: Acoustical Events and Perceptions








The Physical Variables: Early Reflections





Problems with the Stereo Phantom Center Image




The Physical Variables: Loudspeaker Directivity



The Physical Variables: Acoustical Surface Treatments





Absorbers



Engineered Surfaces and Other Sound Scattering/Diffusing Devices




Subjective Evaluations of Physical Variations





Side Wall Treatment: Reflecting or Absorbing –Kishinaga et al. (1979)



The Effect of Loudspeaker Directivity – Toole (1985)



Loudspeaker Directivity and Wall Treatment Together – Choisel (2005)



The Nature of the Sound Field – Klippel (1990)



Observations of an Audio Enthusiast – Linkwitz (2007)



Observations of an Audio Enthusiast – Toole (2016)



Floor Reflections: A Special Case?




Professional vs. Recreational Listening





Hearing Loss is a Major Concern



Discussion




Perceptual Effects of Room Reflections





Adaptation and Perceptual Streaming



The Effect of Rooms on Loudspeaker Sound Quality



The Effect of Rooms on Speech Intelligibility



Sound Localization in Reflective Spaces − The Precedence (Haas) Effect



Bringing the Precedence Effect into the Real Acoustical World





Ceiling vs. Wall Reflections



Real vs. Phantom Images



Speech vs. Various Musical Sounds






Meaningful Measurements of Reflection Amplitudes



Chapter 8: Below the Transition Frequency: Acoustical Events and Perceptions








The Basics of Room Resonances and Standing Waves





Optimizing Room Dimensions – Does an "Ideal" Room Exist?



Are Non-Rectangular Rooms the Answer?




Solutions for the Real World





Deliver Energy to the Modes and Dissipate Some of That Energy with Absorbers



Deliver Energy to the Modes and Reduce the Coupling of That Energy to the Listener By Optimizing the Listening Location – "Positional" Equalization



Reduce the Energy Delivered to a Bothersome Mode by Optimizing the Loudspeaker/Subwoofer Location



Reduce the Energy Delivered to a Bothersome Mode by Using Parametric Equalization



Reduce the Energy Delivered to a Bothersome Mode by Using Simple Mode-Manipulation Techniques



Selective Mode Activation in Rectangular Rooms Using Passive Multiple-Subwoofer Mode Manipulation



Mode Manipulation for Rectangular Rooms Using Multiple Subwoofers and Signal Processing



Mode Manipulation For Any Room Using Multiple Subwoofers and Signal Processing: Sound Field Management (SFM).



Revisiting Room Resonances in Time and Space




Do we Hear the Spectral Bump, the Temporal Ringing, or Both?



Stereo Bass: Little Ado About Even Less



Bass Management Makes it all Possible.



Summary and discussion



Chapter 9: Adjacent boundary and loudspeaker mounting effects








The effects of solid angles on the radiation of sound by omnidirectional sources



Classic adjacent-boundary effects





Alleviating adjacent-boundary effects




Loudspeaker mounting options and effects





An example of adjacent-boundary interference




"Boundary-friendly" loudspeaker designs



Array loudspeakers – other ways to manipulate boundary interactions



Listeners also have boundaries



Chapter 10: The Sound Fields in Sound Reproduction Spaces








Reverberation





Measuring reverberation time



Calculating reverberation time



Is there a more useful metric for our purposes?




Diffusion



Direct sound and early reflections



Near and far fields of rooms − sound level vs. distance



Near and far fields of sound sources





Point sources and real loudspeakers



Line sources




Air absorption at high frequencies



Screen loss in home theaters and cinemas



The directivities of common sound sources



Chapter 11: Sound in cinemas








The closed loop of cinema sound



Sound fields in cinemas





A loudspeaker in a cinema



Adding a screen and applying the X-curve




The origins of the X-curve



A recent study adds confirmation and clarity



Flat, direct sound is an enduring favorite



Alternative targets – is it time to move on?





Compatibility with the rest of the audio world
Compatability with the cinema world




The effects of room size and seats



Cinema sound – where to next



Chapter 12: Sound in home listening rooms, home theaters and recording control rooms








Good sound starts with good loudspeakers





Typical loudspeaker specifications – part of the problem




Loudspeakers in small rooms: the meaning of room curves





The effect of loudspeaker directional configuration



Looking back 42 years: the Møller/Brüel and Kjaer experiments



Room curves and equalization




Subjective preferences for sound spectra in listening rooms



Dialog intelligibility in home theaters



Recording control rooms





Old-school monitoring



Modern monitoring





Chapter 13: A rational approach to designing, measuring and calibrating sound reproducing systems








Low frequencies – the universal problem



Sound above the transition frequency





Thirty years – some things change, some don’t



The wrong room curve target?



"Room correction" and "room equalization" are misnomers.



Automotive audio



Headphones



Cinemas




Is there a common factor – a generalizable target?



Chapter 14: Measurement methods








Alternative views of frequency response





Prediction of the direct sound and room curves from anechoic data



In-situ measurement of the direct sound



The steady-state room curve




Measures of loudness and system level calibrations.





Evaluating relative program loudness levels



Multichannel system level calibration



The effect of propagation distance – a side-channel challenge


Measurement microphones







Chapter 15: Multichannel Audio








A few definitions



The birth of multichannel audio



Stereo – an important beginning





Loudspeakers as stereo image stabilizers




Quadraphonics – stereo times two



Multichannel audio – cinema to the rescue



Multichannel comes home





THX embellishments




How many loudspeakers and where?





Optimizing the delivery of "envelopment"



Summary




Surround system layouts





Loudspeaker directivity requirements



Mission oriented acoustical treatments



Surround loudspeaker options




The Ambisonics alternative



Upmixer manipulations: creative instincts at work



Multichannel audio goes digital, discrete and compressed



Three-dimensional sound – immersive audio





The perception of elevation







Chapter 16: Loudspeakers and Power Amplifiers





Consequence of Loudspeaker Impedance Variations
The Damping Factor Deception
Loudspeaker Sensitivity Ratings and Power Amplifiers
The Audibility of Clipping



Chapter 17: Hearing loss and hearing conservation








Occupational noise exposure limits



Non-occupational noise exposure



Binaural hearing is also affected



Some obsession can be a good thing



Chapter 18: Fifty years of progress in loudspeaker design








My introduction to the real world



Two decades of domestic loudspeakers



Some early professional monitor loudspeakers





A "Toole" monitor loudspeaker




Looking around and looking ahead



The end



References

Index