Transcript Dynamic Range

Advanced Lecture

dynamic range The ratio of the loudest (undistorted)
signal to that of the quietest (discernible) signal in a
unit or system as expressed in decibels (dB).

Dynamic range is another way of stating the
maximum S/N ratio.

With reference to signal processing equipment, the
maximum output signal is restricted by the size of the
power supplies, i.e., it cannot swing more voltage
than is available.
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
While the NOISE FLOOR of the unit determines the
minimum output signal. SMALLEST POSSIBLE
LEVEL

Professional-grade analog signal processing
equipment can output maximum levels of +26 dBu,
with the best noise floors being down around -94
dBu.

This gives a maximum dynamic range of 120 dB –
almost the range of HUMAN HEARING!

dBFS means "decibels relative to full scale".

It is an abbreviation for decibel amplitude
levels in digital systems which have a
maximum available peak level; like PCM
encoding.

VU Reference Level: An analog representation
of digital signal

(Standard setting would be "20 Ref" resulting in
a -20dB FS = 0 VU)

VU Graphic Bar Level Meter: Indicates VU level
of left and right digital audio.
More on Metering

VU Numeric Level Meter: Indicates VU level
of left and right digital audio.

Peak Program Meter: Area above the main
bar indicating peak program levels.

Maximum Peak Level Meter: Displays
maximum or peak level of the audio program
material.

VU meters are designed to represent the
perceived loudness of a passage of music,
measuring in volume units.

The product is designed so that the best signal
quality is obtained when the meter rarely goes
above nominal.

The markings are often in dB instead of "VU",
and the reference level is defined in the
product's manual.

In professional recording and sound
reinforcement gear, the nominal level is
0 VU = +4 dBu.

In consumer level equipment, the
nominal level varies, but some
standardize to 0 VU = −10 dBV.
Consumer vs. Pro


The difference between consumer and pro
equipment revolves around the cost required
to create larger power supplies and output
higher levels
consumer levels can be generated by batterypowered gear, but pro levels require power
supplies

Nominal level is the operating level at which an
electronic signal processing device is designed to
operate.

Electronic circuits are limited in the maximum
signal they can output and the electronic noise
they add to the signal.

The difference between the internal noise and
the maximum output level is the device's
DYNAMIC RANGE.
More on Nominal Level
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When a signal is chained improperly through
many devices, the dynamic range of the signal is
reduced. The nominal level is the level that these
devices were designed to operate at, for BEST
dynamic range.

In audio, a related measurement, signal-to-noise
ratio, is usually defined as the difference
between the nominal level and the noise floor,
leaving the headroom as the difference
between nominal and maximum output.

It is important to realize that the measured level
is a time average, meaning that the peaks of
audio signals regularly exceed the measured
average level.

The headroom measurement defines how far
the peak levels can stray from the nominal
measured level before clipping.

The difference between the peaks and the
average for a given signal is the crest factor.

The crest factor or peak-to-average ratio
(PAR) or peak-to-average power ratio
(PAPR) is a measurement of a waveform,
calculated from the peak amplitude of the
waveform divided by the RMS value of the
waveform.

0 dBFS is assigned to the maximum possible
level in a digital signal
A signal that reaches 50% of the maximum
level would peak at -6 dBFS, for instance.

All peak measurements will be negative
numbers. There are NO Positive Numbers
Dynamic Range Comparison
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AM Radio 20-30 dB
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FM Radio 40-50 dB

Vinyl microgroove phonograph records
typically yield 55-65 dB, though the first play
of the higher-fidelity outer rings can achieve
a dynamic range of 70 dB.
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A dynamic microphone has up to 140 dB
dynamic range, while condenser microphones
are limited by the overloading of their
associated electronic circuitry.
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Practical considerations of acceptable distortion
levels in microphones combined with typical
practices in a recording studio result in a useful
operating range of 125 dB.
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Compact Cassette tape performance ranges
from 50 to 56 dB depending on tape
formulation.

The peak of professional analog magnetic
recording tape technology reached 90 dB
dynamic range in the midband frequencies at
3% distortion, or about 80 dB in practical
broadband applications.[
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Digital audio at 16-bit resolution has a
theoretical dynamic range of 96 dB, but the
actual dynamic range is usually lower
because of overhead from filters that are built
into most audio systems.
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Audio CDs achieve about a 90-dB signal-tonoise ratio.
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What is the Dynamic Range of a 24-bit
recording?
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144 dB! (Compared to 96 dB in 16-bit)
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Limited only by your gear!
The SACD format is capable of delivering a dynamic range
of 120 dB from 20 Hz to 20 kHz and an extended frequency
response up to 100 kHz, although most currently available
players list an upper limit of 80–90 kHz.
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SACD – 120dB
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Human ear – 120dB
What does it all mean?
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The dynamic range from a given signal source
is limited by the WEAKEST signal in the chain
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Mic  Pre-amp  Converter  digital or
analog medium
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Getting closer to 120dB means that our ears
will hear the full dynamic range