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The Exceptional Audio Experience
Audio Experience Hierarchy Transformational Experience Audience Engagement Accuracy: Space, Time & Imaging
Tone & Fidelity
Fundamentals: Level, Coverage, Understanding
Ben Boeshans “The Audio Experience Hierarchy” Idibri 6/4/18 http://www.idibri.com/audio-experience-hierarchy/
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Audio Experience Hierarchy Transformational Experience Audience EXPERIENCE Engagement Right Brain PREREQUISITES Accuracy: Left Brain Space, Time & Imaging
Tone & Fidelity
Fundamentals: Level, Coverage, Understanding
The 5 Questions The 5 Questions: • Is it loud enough? • Can everybody hear? • Can everybody understand? • Will it feed back? • Does it sound good?
Tone & Fidelity
Fundamentals: Level, Coverage, Understanding
Handbook for Sound Engineers: The New Audio Cyclopedia, Chris Foreman (4th Edition page 1239)
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The 5 Questions
Does it sound good?
Everybody Understand? Enough Gain? Loud Enough? Everybody Hear?
AVIXA Standards • Performance Verification Standards • Common Language • Raise the Bar for the AV Industry • Transform Systems into Experiences
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AVIXA Standards
• Loud Enough? • Everyone Hear? • Everyone Understand? • Early Development • Published in 2017 • Public Review
Dynamic Range
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Where we started…
“… audio systems must be capable of accurately representing the original audio source to the listeners. The key to achieving these goals is the dynamic range of the given system. This means that systems must be capable of delivering sufficient loudness to the listener at low distortion and with optimum headroom in the signal chain. Proper attention to these characteristics during design and commissioning will also ensure that systems will provide adequate speech intelligibility throughout the audience area along with accurate reproduction of live or pre-recorded musical sources.”
What is Dynamic Range?
Dynamic range is defined as “The ratio of the largest to the smallest intensity of sound that can be reliably transmitted or reproduced by a particular sound system, measured in decibels.” “Audio systems must be capable of accurately representing the original audio source to the listeners. The key to achieving this goal is the dynamic range of the given system. This means that systems must be capable of delivering sufficient loudness to the listener at low distortion and with optimum headroom in the signal chain. Proper attention to these characteristics during design and commissioning will also ensure that systems will provide adequate speech intelligibility throughout the audience area along with accurate reproduction of live or pre-recorded musical sources.” From the Abstract for AVIXA A104.01:201X, Sound System Dynamic Range As a reference, the dynamic range of our hearing system is approximately 120dB from the threshold of hearing to the loudest sound we can stand.
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Our goals?
• Characterize the required SPL from an audio system, recommend a signal-to-noise ratio (based on the anticipated acoustic ambient noise level in a venue) for different venue types, and provide measurement techniques using commonly available test equipment. • Define the minimum idle noise floor level of the audio system (for lower NC rooms). • Define performance requirements for audio system gain structure for a variety of venues and provide standards for verifying and reporting the levels of the audio system at various stages of the signal path. • Determine an appropriate testing procedure for a system to sustain the specified qualities and characteristics over a defined time scale. • Define the performance metrics to measure the temporal output characteristics of an amplified audio system that will provide high quality, intelligibility, and fidelity
What is dynamic range? • Electrical dynamic range • Signal-to-Noise Ratio + headroom • Starts with EIN – the absolute noise floor • What is the quiescent noise floor of the system with optimized signal-to-noise? • What is the largest voltage output a properly terminated amplifier is capable of? • The difference between those two levels is the electrical dynamic range of the system
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What is dynamic range? • Electroacoustic dynamic range • The difference between the softest sound or signal and the loudest • What is the softest sound? • EIN? • ANL of the room? • ANL of the room with an audience present? • What about concert halls? Recording studios? Sporting events? • What is the loudest sound? • What the loudspeaker system capable of producing at the listener’s ears? • Two key aspects – when and where do you make the measurement?
How do I parse thee? Let me count the ways…
Categories High Background Noise Low Background Noise
Speech • • Conferencing • Full Bandwidth • • Mixed • •
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Venues
• Conference rooms and meeting spaces • Lecture halls and classrooms • Performing arts facilities • Sports facilities • Video teleconferencing systems
What are we doing?
• In the field: • Measure the noise floor of the audio system • Measure the ambient noise floor of the room • Confirm that the system can deliver the required SPL and maintain it for 60 seconds
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The Setup
What does the process look like?
Verify: System gain Verify: Maximize the Ask: Are we connected to structure acoustic output of the anything else? System signal-to-noise system Audio and video Terminate an input Connect the loudspeakers conferencing equipment •Measure EIN Inject a signal (12dB peak- What is 0dBFS? •Measure the voltage output of average level) into the What is the optimum the amplifier into a dummy load system setting for ATC/VTC Record! Raise the input gain until equipment to operate the loudspeakers go into properly to emulate mechanical compression natural speech in the
Step 1 Step 2 Step Back it off until the 3 Step space? compression is less than Measure and record 1dB across the spectrum of the system Measure the output SPL across the bandwidth of the system
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Are we connected to anything else?
What does the process look like? Now use a microphone! Verify: Maximize the Have we achieved our acoustic output of the targets for: system Electronic noise floor? Connect the Acoustical noise floor? loudspeakers Maximum SPL? Inject a signal (12dB peak-average level) into PAG? the system Intelligibility? Raise the input gain until the loudspeakers
Step 4 Step 5 Step go into mechanical 6 Step compression Back it off until the compression is less than 1dB across the spectrum of the system Measure the output SPL across the bandwidth of the system
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Audio Coverage Uniformity
Audio Coverage Uniformity
• AVIXA A102.01:2017 • Can everybody Hear? • Evaluation of Direct Sound to 50 ms • Level Based – Compares level deviations within each octave band at multiple locations – Goal: same perceived sound levels to every listener • Classification based on Coverage Envelope
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Spectral Balance
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Spectral Balance • AVIXA A103.01:201x – Currently in public review • “Can everybody understand?” & “Does it sound good?” • Evaluation based on the direct sound and first 50 ms of early reflections • Tonality based – Same tonal balance within the listening area
Spectral Balance • Performance Classification – Based on tolerance limits for the frequency response (e.g. ±2 dB) • System Classification – Based on the response of the system at low and high frequency limits – “The system classification indicates the frequency range over which the performance classification shall be evaluated” – Full-Bandwidth Systems: 40 Hz to 12.5 kHz – Limited-Bandwidth Systems: 100 Hz to 12.5 kHz – Voice Communication Systems: 200 Hz to 10 kHz
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Standards in Action ACU and Spectral Balance Case Study
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The Room
Common Process ACU and Spectral Balance
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Common Ground
Common Process
Independent Processing
Common Ground
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Before You Begin
• Is the System Ready? – “The system shall be in its intended operating state with confirmation of loudspeaker functionality and polarity as well as adjustments for gain structure, spectral balance, system equalization, and time offset corrections having already been performed.”
Before You Begin
• Will the system be louder than Background Noise? – “In its intended operating state, the system shall be capable of an acoustic output of at least 15 dB above the ambient noise level in each octave band to be tested.”
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Before You Begin
• Is the Room Ready? – “The venue shall be in its intended operating configuration. This means that all construction activity has ceased, room finishes are in place, the room is in its typical seating configuration, and extraneous noise from people or equipment is minimized.”
Measurement Platform
• Frequency response requirements of Class 1 sound level meter systems • Calibrated • No weighting filters • An impulse response measurement windowed to 50 ms
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Evaluate the Room
The Room
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Listener Areas
“Contiguous space(s) intended to be covered by a sound system.”
Evaluate the System
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Pre-Measurement
• Bandwidth • Multiple Configurations • Distributed or Non-Distributed System
Bandwidth ACU Spectral Balance: • Determined Pre-Test • Determined Post-Test • Limited: • Voice Communication: – 250 Hz – 8 kHz – Test 6 Octave Bands • Limited: – 250 Hz – 8 kHz – 100 Hz – 10 kHz • Full • Full – Test 8 Octave Bands – 40 Hz – 12.5 kHz – Add 125 Hz and 16 kHz
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Multiple Configurations
• Divisible Walls • Movable Seating • Portable PA
Distributed or Point Source
Distributed Speaker Systems Point Source (Non-Distributed) Speaker Systems
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Consistent Loudspeaker Spacing
• Qualifications: – The distance from the loudspeaker mounting plane to the listening plane remains constant throughout the space. – The speaker-to-speaker spacing across the listening plane remains constant.
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Almost-Consistent Spacing • Shifts Happen – Take measurement and evaluate impact – Less than 1 dB = disregard shift – Greater than 1 dB = record extra point
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Inconsistent Loudspeaker Spacing
• Examples – Sloped Floor – Varying Ceiling Heights • Measure & report each unique condition
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Point Source Systems
• Single vs. Multi-Channel • Establish Apparent Origin • Supplemental Fill Points
Single vs Multi-Channel
• “Single Channel Loudspeaker System: A loudspeaker system designed so that a single source feed is distributed to all designated coverage areas” • “Multi-channel Loudspeaker System: A loudspeaker system designed so that multiple loudspeaker locations provide coverage to the same listening areas.”
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Things to Ask
• Multiple signal processing paths?
• Does a single signal processing path cover the entire listening area?
Apparent Origin
• “The apparent origin of a point-source system is the physical point in space from which measurement locations for a listening area are determined. It shall be established based upon the system’s topology.”
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Apparent Origin
“Single primary loudspeaker location, the geometric center of the location shall be used”
Apparent Origin
“For a system consisting of multiple primary loudspeaker locations, the apparent origin is the point geometrically-centered between the outer-most loudspeaker locations”
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Apparent Origin
“A multi-channel system will have an Apparent Origin for each channel. They will be measured and classified independently.”
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Establish Measurement Grid
Using the Apparent Origin – 5 degrees Vertical – 20 degrees Horizontal
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ACU Diverges from Spectral Balance
Fill Speakers - ACU
• Two conditions: – “At the overlap in coverage between two fill loudspeakers” – “In the transition zone between the primary loudspeaker system and the fill system where the direct SPL from the primary loudspeaker system and the direct SPL from the fill system create the greatest summation or cancellation” • Required horizontally and vertically
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Fill Loudspeaker Systems – Spectral Balance • “A set of loudspeakers that supplement sound from the main loudspeakers, such as under or over balcony loudspeakers.” • Fill loudspeaker systems require a secondary set of measurement locations. • Exception: “Front-fill loudspeaker systems do not require a secondary measurement grid and shall be measured as part of a non-distributed loudspeaker system.” • The secondary measurement grid is very similar to the primary measurement grid for the main loudspeaker system.
Secondary Measurement Grid
Horizontal Grid, 20°
Apparent Origin
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Secondary Measurement Grid
5° Vertical Grid for Balcony
5° Vertical Grid for Under-Balcony
Primary Measurement Grid
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Eliminate Closely-Spaced Points
If multiple measurement locations are calculated to be within a 2 m (6.5 ft.) radius, the location farthest from the other remaining measurement locations shall be used. The desire is to have maximum spacing between adjacent measurement locations.
A primary point from the main loudspeaker system shall not be deleted to defer to a secondary point from the fill loudspeaker system.
Eliminate Closely-Spaced Points
Original Primary Points: 31 Eliminated: 11 Remaining: 20
Original Secondary Points : 16 Eliminated: 9 Remaining: 7
Some additional secondary locations under the balcony Probably 5 to 7 points
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Test
Setting Up the Test
• Stimulus – Pink Noise – Swept Sine • Ambient Noise Level – Add 15 dB for stimulus level • Verify Headroom • Transfer the Grid
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Ambient Noise Level
Process the Data
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50 ms IR Window
Impulse Response
50 ms IR Window
Same data shown as an ETC (Envelope Time Curve)
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Independent Processing
Independent Processing
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Process the Data
• Dependent on program’s output • Requirements – 50 ms Window – Octave Band Data • Otherwise = Process
Process the Data
) ) *+ */ • 10 log&'(10 +, + ⋯ + 10 +, ) • Where:
– 12+ = 45654 75189:; 1< 4=>57 ?1:8 49@9t, 9: 85B9?54
– 12/ = 45654 75189:; 1< CDD57 ?1:8 49@9<, 9: 85B9?54
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Process the Data
Converts from Logarithmic to Linear Power SUM formula
)*+ )*. 10 log&'(10 &' + ⋯ + 10 &' )
Converts back to All of the fractional- Logarithmic from Linear octave data within the given one-octave band
Record the Data
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Classification
System Classification
3dB
6dB
8dB The system classification will be greater than or equal to the octave band with the greatest coverage envelope 12dB
> 12dB
Independent Processing
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Process the Data • Apply a 50 ms impulse response window to each measurement • Match the broad-band level of all the measurements – 250 Hz to 8 kHz octave bands (225 Hz to 8.8 kHz) • Power average all the measurements (magnitude only) • Apply one-octave smoothing to the resultant magnitude response • Normalize the magnitude response to 0 dB at 1 kHz • Apply tolerance limits
Level Match the Measurements
110
105
100
95
90
85
80
75 Sound pressure, Level [dB]
70
65
60 20 50 100 200 500 1k 2k 5k 10k 20k
Frequency [Hz]
Not Level Matched
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Level Match the Measurements
110
105
100
95
90
85
80
75 Sound pressure, Level [dB]
70
65
60 20 50 100 200 500 1k 2k 5k 10k 20k
Frequency [Hz]
Level Matched
Level Match the Measurements
110
105
100
95
90
85
80
75 Sound pressure, Level [dB]
70
65
60 20 50 100 200 500 1k 2k 5k 10k 20k
Frequency [Hz]
Not Level Matched
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Level Match the Measurements
110
105
100
95
90
85
80
75 Sound pressure, Level [dB]
70
65
60 20 50 100 200 500 1k 2k 5k 10k 20k
Frequency [Hz]
Level Matched
Power Average the Measurements
110
105
100
95
90
85
80
75 Sound pressure, Level [dB]
70
65
60 20 50 100 200 500 1k 2k 5k 10k 20k
Frequency [Hz]
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Apply one-octave smoothing
110
105
100
95
90
85
80
75 Sound pressure, Level [dB]
70
65
60 20 50 100 200 500 1k 2k 5k 10k 20k
Frequency [Hz]
Tolerance Limits
12
10
8
6 4 SB-A: ±2 dB 2 0 SB-B: ±3 dB -2
-4
Sound pressure, Level [dB] SB-C: ±4 dB -6
-8
-10 SB-D: ±5 dB
-12 20 50 100 200 500 1k 2k 5k 10k 20k
Frequency [Hz]
Full Bandwidth: 40 Hz to 12.5 kHz Limited Bandwidth: 100 Hz to 12.5 kHz
Voice Communication: 200 Hz to 10 kHz
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Normalize 1 kHz to 0 dB
12
10
8
6
4
2 0 SB-B: ±3 dB -2
-4 Sound pressure, Level [dB] -6
-8
-10
-12 20 50 100 200 500 1k 2k 5k 10k 20k
Frequency [Hz]
Limited Bandwidth: 100 Hz to 12.5 kHz SB-B - Limited
Audio Fundamentals
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Audio Experience Hierarchy Transformational Experience Audience EXPERIENCE Engagement Right Brain PREREQUISITES Accuracy: Left Brain Space, Time & Imaging
Tone & Fidelity
Fundamentals: Level, Coverage, Understanding
AVIXA Standards
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What do you think?
Get Involved! • AVIXA.org/standards • [email protected]
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Contact Us
Thom Mullins Charlie Hughes Ben Boeshans [email protected] [email protected] [email protected]
The Exceptional Audio Experience
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