IEC TS 63001:2019

IEC TS 63001 ®
Edition 1.0 2019-01
TECHNICAL
SPECIFICATION
colour
inside
Measurement of cavitation noise in ultrasonic baths and ultrasonic reactors
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IEC TS 63001 ®
Edition 1.0 2019-01
TECHNICAL
SPECIFICATION
colour
inside
Measurement of cavitation noise in ultrasonic baths and ultrasonic reactors

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.01; 17.140.50 ISBN 978-2-8322-6410-2

– 2 – IEC TS 63001:2019 © IEC 2019
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 List of symbols . 11
5 Measurement equipment . 11
5.1 Hydrophone . 11
5.1.1 General . 11
5.1.2 Calibration of hydrophone sensitivity . 12
5.1.3 Hydrophone properties . 12
5.1.4 Hydrophone compatibility with environment . 12
5.2 Analyser . 13
5.2.1 General considerations . 13
5.2.2 Specific measurement method: transient cavitation spectrum at f =
2,25 f . 14
5.2.3 Specific measurement method: broadband transient and stable
cavitation spectra . 14
5.3 Requirements for equipment being characterized . 14
5.3.1 Temperature and chemistry compatibility with the hydrophone . 14
5.3.2 Electrical interference . 14
6 Measurement procedure . 14
6.1 Reference measurements . 14
6.1.1 Control of environmental conditions for reference measurements . 14
6.1.2 Measurement procedure for reference measurements . 15
6.2 Measurement procedures for in-situ monitoring measurements . 15
Annex A (informative) Background . 16
A.1 Cavitation in ultrasonic cleaning . 16
A.2 Practical considerations for measurements . 18
A.3 Measurement procedure in the ultrasonic bath . 19
A.4 Characterization methods that do not utilize the acoustic spectrum . 20
Annex B (normative) Cavitation measurement at 2,25 f . 21
B.1 General . 21
B.2 Measurement method . 21
Annex C (informative) Example of cavitation measurement at 2,25 f . 24
Annex D (normative) Cavitation measurement by extraction of broadband spectral
components . 25
D.1 Compensation for extraneous noise . 25
D.2 Features of the acoustic pressure spectrum . 25
D.3 Identification of the operating frequency f and direct field acoustic pressure . 26
D.3.1 Identification of the operating frequency f . 26
D.3.2 Fit to primary peak (direct field) . 26
D.3.3 Determination of RMS direct field acoustic pressure . 26
D.3.4 Validation . 26
D.4 Identification of stable and transient cavitation component . 26
D.4.1 Subtraction of direct field component of spectrum . 26

D.4.2 Determination of stable cavitation component . 26
D.4.3 Determination of transient cavitation component . 26
D.4.4 Validation . 27
Bibliography . 28

Figure A.1 – Typical setup of an ultrasonic cleaning device . 16
Figure A.2 – Spatial distribution of the acoustic pressure level in water in front of a 25
kHz transducer with reflections on all sides of the water bath (0,12 m × 0,3 m × 0,25 m) . 17
Figure A.3 – Typical Fourier spectrum for sinusoidal ultrasound excitation above the
cavitation threshold at an operating frequency of 35 kHz . 17
Figure A.4 – Sketch of cavitation structure under the water surface at an operating
frequency of 25 kHz . 18
Figure A.5 – Typical rectangular ultrasound signal with a frequency of 25 kHz and 50
Hz double half wave modulation . 19
Figure B.1 – Block diagram of the measuring method of the cavitation noise level L . 22
CN
Figure C.1 – Power dependency of the cavitation noise level L . 24
CN
Figure D.1 – Schematic representation of acoustic pressure spectrum . 25
Pf()
RMS
– 4 – IEC TS 63001:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT OF CAVITATION NOISE IN ULTRASONIC
BATHS AND ULTRASONIC REACTORS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a Technical
Specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical Specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
Technical Specification IEC 63001 has been prepared by IEC technical committee 87:
Ultrasonics.
The text of this Technical Specification is based on the following documents:
Draft TS Report on voting
87/681/DTS 87/693A/RVDTS
Full information on the voting for the approval of this Technical Specification can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
Terms in bold in the text are defined in Clause 3.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• transformed into an International Standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC TS 63001:2019 © IEC 2019
INTRODUCTION
Ultrasonically induced cavitation is used frequently for immersion cleaning in liquids. There
are two general classes of ultrasonically induced cavitation. Transient cavitation is the rapid
collapse of bubbles. Stable cavitation refers to persistent pulsation of bubbles as a result of
stimulation by an ultrasonic field. Both transient cavitation and stable cavitation may create
significant localized streaming effects that contribute to cleaning. Transient cavitation
additionally causes a localized shock wave that may contribute to cleaning and/or damage of
parts. Both types of cavitation create acoustic signals which may be detected and measured
with a hydrophone. This document provides techniques to measure and evaluate the degree
of cavitation in support of validation efforts for ultrasonic cleaning tanks and cleaning
equipment, as used, for example, for the purposes of industrial process control or for hospital
sterilization.
MEASUREMENT OF CAVITATION NOISE IN ULTRASONIC
BATHS AND ULTRASONIC REACTORS
1 Scope
This document, which is a Technical Specification, provides a technique of measurement and
evaluation of ultrasound in liquids for use in cleaning devices and equipment. It specifies
• the cavitation measurement at 2,25 f in the frequency range 20 kHz to 150 kHz, and
• the cavitation measurement by extraction of broadband spectral components in the
frequency range 10 kHz to 5 MHz.
This document covers the measurement and evaluation of the cavitation, but not its
secondary effects (cleaning results, sonochemical effects, etc.).
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
averaging time for cavitation measurement
t
av
length of time over which a signal is averaged to produce a measurement of cavitation
Note 1 to entry: Averaging time for cavitation is expressed in seconds (s).
3.2
cavitation
formation of vapour cavities in a liquid
3.2.1
transient cavitation
inertial cavitation
sudden collapse of a bubble in a liquid in response to an externally applied acoustic field,
such that an acoustic shock wave is created
3.2.2
stable cavitation
oscillation in size or shape of a bubble in a liquid in response to an externally applied acoustic
field that is sustained over multiple cycles of the driving frequency

– 8 – IEC TS 63001:2019 © IEC 2019
3.3
end of cable loaded sensitivity
M ( f )
L
modulus quotient of the Fourier transformed
output voltage U( f ) at the end of any integral cable or output connector of a hydrophone or
hydrophone-assembly, when connected to a specific electric load impedance, to the Fourier
transformed acoustic pressure P(f ) in the undisturbed free field of a plane wave in the position
of the reference centre of the hydrophone if the hydrophone were removed, at a specified
frequency
Note 1 to entry: The Fourier transform is in general a complex-valued quantity but for this document only the
modulus is considered, and is expressed in volt per pascal, V/Pa,
Note 2 to entry: The term ‘response’ is sometimes used instead of ‘sensitivity’.
3.4
end of cable loaded sensitivity level
M
L.dB
twenty times the logarithm to the base 10 of the ratio of the modulus of the end of cable
loaded sensitivity M ( f ) to a reference sensitivity of M .
L ref
M
L
Note 1 to entry: M = 20log dB .
L,dB 10
M
ref
Note 2 to entry: The value of reference sensitivity M is 1 V/Pa.
ref
3.5
hydrophone
transducer that produces electric signals in response to waterborne acoustic signals
[SOURCE: IEC 60050-801:1994, 801-32-26] [1]
3.6
hydrophone assembly
combination of hydrophone and hydrophone pre-amplifier
[SOURCE: IEC 62127-3: 2007, 3.10] [2]
3.7
number of averages
N
av
number of waveforms captured and averaged in a cavitation measurement
3.8
operating volume
part of the liquid volume where cavitation effects are intended
3.9
operating frequency
f
driving frequency of ultrasound generator
Note 1 to entry: Operating frequency is expressed in hertz (Hz).
3.10
relative cavitation measurements
measurements made for purposes of comparison between two different cleaning
environments or different locations within a cleaning environment, such that the end-of-cable
loaded sensitivity of the hydrophone may be assumed to be identical in both cases

Note 1 to entry: Care should be taken to ensure that changes in hydrophone sensitivity do not affect the
measurement.
3.11
sampling frequency
f
s
number of points per second captured by a digital waveform recorder
Note 1 to entry: Sampling frequency is expressed in hertz (Hz).
3.12
size of the capture buffer
N
cap
total number of points captured at a time by a digital waveform recorder
3.13
capture time
t
cap
length of time to capture N points at a sampling frequency of f
cap s
Note 1 to entry: Capture time is expressed in seconds (s).
3.14
cavitation noise level
L
CN
level calculated from the cavitation noise at a frequency of 2,25 f
Note 1 to entry: Cavitation noise is expressed in decibels (dB).
3.15
reference sound pressure
P
ref
sound pressure, conventionally chosen, equal to 20 μPa for gases and to 1 μPa for liquids
and solids
Note 1 to entry: Reference sound pressure is expressed in pascals (Pa).
[SOURCE: IEC 60050-801:1994, 801-21-22] [1]
3.16
averaged power spectrum
P f
( )
power spectrum of the instantaneous acoustic pressure averaged over N measurements
av
Note 1 to entry: Averaged power spectrum is expressed in Pa .
3.17
median of acoustic pressure
P
n
median value of amplitude values of spectral lines within B
f
Note 1 to entry: Median of acoustic pressure is expressed in pascals (Pa).
3.18
band filter
B
f
band filter located at a centre frequency of 2,25 f
Note 1 to entry: Band filter is expressed in hertz (Hz).

– 10 – IEC TS 63001:2019 © IEC 2019
3.19
direct field acoustic pressure
P
portion of the RMS acoustic pressure signal arising directly from the ultrasonic driving
excitation, at the operating frequency of the device
Note 1 to entry: RMS direct field acoustic pressure is expressed in pascals (Pa).
3.20
spectral acoustic pressure
P( f )
Fast Fourier Transform of the hydrophone voltage divided by the end-of-cable loaded
sensitivity
Note 1 to entry: Spectral acoustic pressure is expressed in pascals (Pa).
3.21
stable cavitation component
P
s
portion of the RMS acoustic pressure signal arising from stable cavitation
Note 1 to entry: The stable cavitation component is expressed in pascals (Pa).
3.22
transient cavitation component
P
t
portion of the RMS acoustic pressure signal arising from transient cavitation
Note 1 to entry: The transient cavitation component is expressed in pascals (Pa).
3.23
voltage
u(t)
instantaneous voltage measured by analyser
Note 1 to entry: Voltage is expressed in volts (V).
3.24
voltage spectrum
U(f)
Fast Fourier Transform of the voltage
Note 1 to entry: Voltage spectrum is expressed in volts (V).
3.25
frequency spacing
∆f
distance of spectrum samples of a Fast Fourier Transform
Note 1 to entry: Frequency spacing is expressed in hertz (Hz).
3.26
indexed frequency
f
k
frequency of index k at which the Fast Fourier Transform is evaluated
Note 1 to entry: f (k – 1) ∆f, where k = 1, 2, …, N .
k cap
4 List of symbols
f frequency
f indexed frequency
k
f operating frequency
f sampling frequency
s
M ( f ) end-of-cable loaded sensitivity
L
N number of averages
av
N number of points captured in a waveform
cap
t capture time
cap
P( f ) spectral acoustic pressure (a function of frequency)
( f ) direct field acoustic pressure
P
P ( f ) stable cavitation component
s
P ( f ) transient cavitation component
t
u(t) voltage (a function of time)
U( f ) voltage spectrum (a function of frequency)
L cavitation noise level
CN
P reference sound pressure
ref
P f averaged power spectrum
( )
P median of acoustic pressure
n
B band filter
f
T averaging time for cavitation measurement
av
∆f frequency spacing
5 Measurement equipment
5.1 Hydrophone
5.1.1 General
It is assumed throughout this document that a hydrophone is a device which produces an
output voltage waveform in response to an acoustic wave. Specifically, for the case of a
sinusoidal acoustic wave, the hydrophone shall produce an output voltage proportional to the
acoustic pressure integrated over its electro-acoustically active surface area. Assuming that
spatial variations in the acoustic pressure field over this active surface area are negligible, the
hydrophone may then be assumed to be a point sensor and the acoustic field pressure may
be described by Equation (1):
Pf()= U()f / M ()f (1)
L
where Pf() is the amplitude of the acoustic field pressure, Uf() is the amplitude of the
voltage, and M (f) is the end-of-cable loaded sensitivity of the hydrophone (defined also as
L
an amplitude for the purposes of this document). All parameters are expressed as a function
of frequency and follow the convention of only designating the magnitude of frequency-
dependent quantities, disregarding their phase angle.

– 12 – IEC TS 63001:2019 © IEC 2019
5.1.2 Calibration of hydrophone sensitivity
The hydrophone shall be calibrated such that M (f), the end-of-cable loaded sensitivity of
L
the hydrophone, is known for any frequency or frequency component for which an acoustic
pressure value is reported.
NOTE In some cases cavitation measurements can be made in relative terms, in which case a calibration to
determine M (f) is not necessary. See 5.2.1.3.
L
5.1.3 Hydrophone properties
5.1.3.1 Acoustic pressure range
The hydrophone and any associated electronics shall be suitable for the maximum pressure
of the environment, and shall be at minimum suitable for an RMS acoustic pressure up to
600 kPa.
5.1.3.2 Bandwidth of the hydrophone
(f),
The bandwidth of the hydrophone should be according to 5.1.2, such that variations in M
L
the end-of-cable loaded sensitivity of the hydrophone, may be compensated for by the
cavitation measurement scheme, such as in 5.2.1.4.
5.1.3.3 Directional response
The hydrophone shall have an approximately spherical directivity. In order to achieve this,
for an operating frequency below 100 kHz the hydrophone should have an effective diameter
less than a quarter wavelength. This guideline may be relaxed above 100 kHz because of the
potential difficulty in achieving such a small effective diameter in a package that can
withstand the cleaning environment; however, there is the corresponding increase in
measurement uncertainty and the user should attempt to account for it.
5.1.3.4 Cable length
A connecting cable of a length and characteristic impedance which ensure that electrical
resonance in the connecting cable does not affect the defined bandwidth of the hydrophone
or hydrophone-assembly shall be chosen. The cable shall also be terminated appropriately.
To minimize the effect of resonance in the connecting cable located between the
hydrophone’s sensitive element and a preamplifier or waveform digitizer input, the numerical
+ BW ) where f is
value of the length of that cable in metres shall be much less than 50/(f
0 20 0
the operating frequency in megahertz and BW is the -20 dB bandwidth of the
hydrophone signal in megahertz.
Attention should be paid to the appropriateness of the output impedance of the
hydrophone/amplifier in relation to the input impedance of the connected measuring device.
5.1.3.5 Measurement system linearity
The user shall ensure that the voltage output of any preamplifier or amplifier is linear over the
range used. This shall be done by obtaining the maximum voltage output within which the
response is linear within 10 %, and providing necessary adjustments to gain, such as may be
available from gain control settings on the preamplifier or amplifier.
5.1.4 Hydrophone compatibility with environment
Environmental conditions such as temperature or the chemistry of the environment shall be
within the hydrophone manufacturer’s stated range of operating conditions.

Differences between the calibration conditions for the hydrophone and the measurement
conditions shall be considered to the extent that they may affect the measurements. For
example, for relative cavitation measurements made at the same temperature with
hydrophones of identical construction, it may not be necessary to determine how the
sensitivity of the hydrophone changes between the calibration and measurement conditions.
However, for absolute measurements the change in hydrophone sensitivity with temperature
shall be known, and corrected for in accordance with IEC 62127-3:2007.
5.2 Analyser
5.2.1 General considerations
5.2.1.1 General
The analyser is an instrument that converts u(t), the time-domain voltage waveform provided
by the hydrophone, to a measurement of cavitation activity. 5.2.1 describes several
considerations that are independent of the measuring method. Following that, several
independent methods are described in 5.2.2 to 5.2.3
5.2.1.2 General considerations: sampling rate
If the analyser utilizes digital recording of u(t), let u(t ), designate this sampling with t
m m
designating the discrete points in time captured, with m = 1 … N where N is the size of
cap cap
the capture buffer. The interval in time between successive samples shall be uniform, and
the sampling frequency f shall be at least a factor of two (2) higher than the highest
s
...