Phase angle, time delay and frequency formula angle current voltage phi phase between voltage oscilloscope measure two signals phase lag time shift time difference - sengpielaudio
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Phase in Acoustics
Calculation of phase anglephase difference
phase shift from time delay, time of arrival difference, and frequency
Sound delay time = Time Delay Δ t (time difference) oscilloscope - Phase lag istime shift
Connection between phase, phase angle, frequency, time of arrival Δ t (delay), and ITD
Corner frequency = cut-off frequency = crossover frequency and ITD = Interaural Time Delay
Question: What is the formula for the phase of a sine wave?
There is no phase of a sine wave. A sine wave has no phase.
A phase can only develop between two sine waves.

Two sine waves are mutually shifted in phase, if the time points
of its zero passages do not coincide.

The word phase has a clear definition for two pure traveling AC sinusoidal waves,
but not for music signals.
All equalizers shift phase with frequency. Without any
fixed-point no "shifting" (displacement) is possible.
Special tricks:
90° filter with two allpass filters. Phases are always phase differences.
Polarity reversal (pol-rev) is never phase shift on the time axis t.
Sinusoidal waveforms of the same frequency can have a phase difference.
If there is a phase shift (phase difference) or phase delay of the phase angle φ
(Greek letter Phi) in degrees it has to be specified between which
pure signals
(sine waves) this appears. Thus, for example, a phase shift can be between the two stereo
channel signals left and right, between the input and output signal, between voltage and
current, or between sound pressure p and velocity of the air particles

What is actually an amplitude?

Sinosoidial Wave
One complete cycle of the wave is associated with an "angular" displacement of
π radians.               omega
The phase φ is the angle of a signal portion, it is specified in angular degrees and
provides a reference to the reference value of the entire signal. For periodic signals is the
total phase angle of 360 degrees and a period equal to the period duration.
A typical question: What is the frequency and the phase angle of a sinusoidal waveform?
Does "one" signal can really have a phase?

Two "in-phase" waves have a phase (angle) of φ = 0 degrees.
If the frequency = 0 Hz, then there is no AC voltage - that's just DC. Then there will be no
phase angle present.

What has time delay to do with phase angle?

Frequency f   Hz
Time delay Δ t   ms
 Phase difference φ in degrees   ° or deg 
φ in radians    rad
 c = 343 m/s at 20°   wavelength λ   m
Calculation between phase angle φ° in degrees (deg), the time delay Δ t and the
f is:
Phase angle (deg)   Phase-Laufzeit
(Time shift) Time difference    Laufzeit-Phase
Frequency   Frequenz-Phase
λ = c / f  and  c = 343 m/s at 20°C.

Calculation between phase angle φ in radians (rad), the time shift or time delay Δ t,
and the frequency f is:

Phase angle (rad)   Bogen-Laufzeit
"Bogen" means "radians". (Time shift) Time difference Laufzeit-Bogenwinkel
Frequency   Frequenz-Bogenwinkel
Time = path length / speed of sound

The time difference (duration) of sound per meter
Effect of temperature on the time difference Δ t
Dependence of the speed of sound only on the temperature of the air

of air in °C
Speed of sound
c in m/s
 Time per 1 m 
Δ t in ms/m
+40 354.9 2.818
+35 352.0 2.840
+30 349.1 2.864
+25 346.2 2.888
+20  343.2 2.912
+15 340.3 2.937
+10 337.3 2.963
  +5 334.3 2.990
  ±0 331.3 3.017
  −5 328.2 3.044
−10 325.2 3.073
−15 322.0 3.103
−20 318.8 3.134
−25 315.7 3.165
 Sound engineers take usually the rule of thumb:
 For the distance of
r = 1 m the sound needs about t = 3 ms in air.
 Δ t = r / c and r = Δ t × c       Speed of sound c = 343 m/s at 20°C.
For a fixed time delay of Δ t = 0.5 ms we get
the following phase shift φ° (deg) of the signal:
Phase difference
φ° (deg)
Phase difference
φBogen (rad)
λ = c / f
360°   2 π = 6.283185307   2000 Hz 0.171 m
180°    π = 3.141592654  1000 Hz 0.343 m
   90° π / 2 = 1.570796327     500 Hz 0.686 m
   45° π / 4 = 0.785398163      250 Hz 1.372 m
      22.5° π / 8 = 0.392699081     125 Hz 2.744 m
        11.25° π /16= 0.196349540    62.5 Hz 5.488 m

Conversion: radians to degrees and vice versa

Phase angle: φ° = 360 × f × Δ t       For time-based stereophony Δ t = a × sin α / c
Frequency f = φ° / 360 × Δ t

Phase angle (deg) φ = time delay Δ t × frequency f × 360
If you take the time difference Δ t = path length a / speed of sound c, then we get
Phase difference φ° = path length
a × frequency
f × 360 / speed of sound c

Please enter two values, the third value will be calculated

Phase angle (deg) φ  ° Magisches Dreieck Ohm
 (Time shift) time delay Δ t  ms
Frequency f  Hz

Some more help: Time, Frequency, Phase and Delay

By Lord Rayleigh (John William Strutt, 3rd Lord Rayleigh, 1907) the duplex theory
was shown. This theory contributes to understanding the procedure of "natural
hearing" with humans. It is the very simple realization that the interaural time of arrival
differences ITD are important at frequencies below 800 Hz as
phase differences
with the localization direction as ear signals, while at frequencies above 1600 Hz
only the interaural level differences ILD are effective.
Between the ears the maximum delay amounts to 0.63 ms. Phase differences for
individual frequencies can be calculated.

Phase shifter circuit for phase angles from φ = 0° to 180°
Voltage vectors of the phase shifter

Phase shifter circuit        Voltage vectors

For R = 0 ohm is VOUT = VIN. The output should not be loaded by low impedance.

You can shift single pure frequencies (sine waves),
but that is impossible with this schematics for music programs.

Two sine voltages - phase shifted: φ = 45°

45° phase shifted

Conditions for distortion-free transmission
From Schoeps - Joerg Wuttke: "Mikrofonbuch" - Chapter 7

The Phase
While the demand for a constant frequency response is clear, the "linear" phase needs rather
There are engineers who expect the ideal phase as constant like the amplitude response.
That is not true. Initially, the phase begins at 0° because the lowest frequency ends at 0 Hz, at
DC. (There is no phase angle between DC voltages).
In the course at a given frequency a phase angle is without meaning, if the phase angle is
only twice as large in the case of double frequency, and three times as large in triplicate, etc.

Courtesy of David Moulton Laboratories
(About Comb Filtering, Phase Shift and Polarity Reversal)

Delay line

Electronic equivalent of the flow of a signal and its delayed iteration, recombined into a
single signal. In the case we will be looking at, the delay line has a delay of 1 millisecond,
the levels of both the original and delayed signals going into the mixer are equal, and the
signal is a 1 kHz sine wave.

Delayed signal

A sine wave of 1500 Hz. frequency (period T = 0.667 ms) and its delayed
iteration, at 1 ms delay. The resulting mixed signal will be a signal with no
amplitude, or a complete cancellation of signal.

Phase Shift
The phase shift for any frequency with a delay of 1 millisecond. The diagonal line
represents the increasing phase shift as a function of frequency. Note that we can
think of 540° as being effectively the same as 180°.

Time, Phase, Frequency, Delay - An audio signal theory primer/refresher

Polarity reversal is no Phase shift of 180° (time delay)

Ř (phi) = phase shift, phase shifting, phase difference, displacement of phase,
phase lag, phase angle are often not correct used as:pol-rev = polarity reversal.
"It was the nightingale, and not the lark". From: Romeo and Juliet, Act 3, Scene 5, William Shakespeare.
It is the "POL-REV" button (polarity reversal) and not the "Phase (shift)" button.

1. Generating a comb filter response
2. "Polarity" and "Phase"
Reverse polarity and phase shift are different terms (German)
Reverse polarity is swapping the wires a/b to b/a (German)
Phase shift as opposed to reversed polarity (German)
Time difference Δ t and phase shift Δ φ (German)

Polarity and phase are often used as if they mean the same thing. They are not.
The "phase reverse button" does not change the phase. It reverses the polarity.

Polarity reversal is no phase shift.
Polarity reversal (or Pol-Rev) is a term that is often confused with phase Ø (phi)
but involves no phase shift or time delay. Polarity reversal occurs whenever we
"change the sign" of the amplitude values of a signal. In the analog realm this
can be done with an inverting amplifier, a transformer, or in a balanced line by
simply switching connections between pins 2 and 3 (XLR plug) on one end of
the cable. In the digital realm, it is done by simply changing all pluses to
minuses and vice versa in the audio-signal data stream.

Two sawtooth oscillations

Polarity reversed signal  top: the original signal a/b (saw tooth)
 middle: the 180° phase shifted signal
 as T/2 time shifted sawtooth

 bottom: the b/a-polarity reversed (inverted) signal,
 mirrored on the time axis
Clearly can be seen that reversed polarity cannot be the same as out of phase.
It is about the much-discussed topic: "Phase shift vs. inverting a signal" and "phase
shift vs. time shift of a signal." The term phase shift is supposedly defined only for
mono frequency sine signals and the phase shift angle is explicitly defined only for
sinusoidal quantities.

The typical Ø (phi)-button is only a polarity changer
There is absolutely no phase shifting

Polarity reversal
Note: Time, frequency and phase belong close together.
The height of the amplitude has no influence on those parameters.

Another thing is the 6 dB per octave roll-off of an electronic RC filter
circuit which is damping the amplitude by 3 dB at the cutoff frequency.
The phase shift is there always 45°.

RC Filter and Cutoff frequency:
Frequency response and equalization EQ:
Phase and amplitude: Filter (RC pad) with 6 dB per octave

The Angular Frequency is ω = 2π × f

Given is the equation: y = 50 sin (5000 t)
Determine the frequency and the amplitude.
Answer: The amplitude is 50 and
ω = 5000.
So the frequency is f = 1/T = ω / 2 π = 795.77 Hz.

To use the calculator, simply enter a value.
The calculator works in both directions of the

Frequency f
 ↔  Angular Frequency ω
ω = 2π × f                              f = ω / 2π
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