Oluschinski at 13:27, 12 December 2025

2025-12-12T13:27:19Z

← Older revision		Revision as of 15:27, 12 December 2025
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	* [[Transmission Light\|Transmission light]]		* [[Transmission Light\|Transmission light]]
	* [[Non-~~desdructive~~ Polymer Testing\|Non-~~desdructive~~ polymer testing]]		* [[Non-destructive Polymer Testing\|Non-destructive polymer testing]]
	* [[Velocity]]		* [[Velocity]]
	* [[Ultrasonic Direct Coupling\|Ultrasonic direct coupling]]		* [[Ultrasonic Direct Coupling\|Ultrasonic direct coupling]]
	* [[Ultrasonic ~~Birefrigence~~\|Ultrasonic ~~birefrigence~~]]		* [[Ultrasonic Birefringence\|Ultrasonic birefringence]]

Oluschinski: Created page with "{{Language_sel|LANG=ger|ARTIKEL=Transmission Schallwellen}} {{PSM_Infobox}} Transmission sound waves FORCETOC ==Fundamentals of transmission== Alongside reflection and absorption, the transmission of sound waves is a phenomenon that occurs at the external or internal boundary surfaces of components or test pieces. In Ultrasound T..."

2025-12-08T06:51:37Z

Created page with "{{Language_sel|LANG=ger|ARTIKEL=Transmission Schallwellen}} {{PSM_Infobox}} Transmission sound waves __FORCETOC__ ==Fundamentals of transmission== Alongside reflection and absorption, the transmission of sound waves is a phenomenon that occurs at the external or internal boundary surfaces of components or test pieces. In Ultrasound T..."

New page

{{Language_sel|LANG=ger|ARTIKEL=Transmission Schallwellen}}
{{PSM_Infobox}}
Transmission sound waves
__FORCETOC__

==Fundamentals of transmission==

Alongside [[Reflection Sound Waves|reflection]] and [[Absorption Sound Waves|absorption]], the transmission of sound waves is a phenomenon that occurs at the external or internal [[Phase Boundary Surface|boundary surfaces]] of components or test pieces. In [[Ultrasound Testing|ultrasonic testing technology]], penetration testing is often also referred to as ultrasonic transmission technique.

Transmission is essentially a [[Material Parameter|parameter]] for electromagnetic waves (e.g. sound waves) that describes the permeability of a medium or material and its [[Phase Boundary Surface|interfaces]] for these waves. The interface itself is formed by adjacent layers (e.g. metal or air with water) that have different characteristic sound impedances or sound impedances ''W'' or ''Z''.

An incident sound wave is partially reflected at an interface and partially transmitted or transferred to the neighbouring layer (cross-coupling). The prerequisite for this is that both neighbouring layers have different sound impedances ''W'', whereby it is not the absolute value but the difference in sound impedances Δ''W'' that is decisive.

==Sound wave resistance or characteristic acoustic impedance==

The sound wave resistance or characteristic impedance of [[Material & Werkstoff|materials]], calculated as the product of [[Density|density]] ''ρ'' and [[Sound Velocity|sound velocity]] ''c'' with ''Z'' or ''W'' = ''ρ'' ''c'', is particularly important for the [[Reflection Sound Waves|reflection]] and transmission behaviour of sound waves. This parameter describes the typical elastic properties of [[Material & Werkstoff|materials]], whereby materials with a high ''W'' value are described as sound-hard (Fe, Cu, Ni) and those with low ''W'' values (PMMA, Al, H2O) as sound-soft [1–4]. If the [[Absorption Sound Waves|absorption of the ultrasonic wave]] is neglected, then depending on the ratio of ''W''1 (sound-hard) to ''W''2 (sound-soft) at the interface, only transmission and [[Reflection Sound Waves|reflection]] occur ('''Fig. 1''').

[[File:Reflection Sound-1.jpg]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px"|[[Reflection Sound Waves|Reflection]] and transmission at the [[Phase Boundary Surface|interface]] between two media a) and between the [[Ultrasonic Sensors|ultrasonic sensor]] and the workpiece surface b) with perpendicular sound incidence [7]
|}

The transmission part is greater the smaller the differences between the sound impedances ''W''1 and ''W''2. However, if the difference between ''W''1 and ''W''2 is very large, as is the case with vacuum or air as the second medium, for example, then a high to total part of the incident sound wave is reflected and no transmission occurs. This effect has a major influence on the detectability of defects in [[Ultrasound testing|ultrasound testing]], both in the [[Ultrasonic Transmission Technique|ultrasonic transmission technique]] and [[Pulse-Echo Ultrasonic Technique|pulse-echo ultrasonic technique]].

==Transmission degree and transmission factor==

In general, the transmission degree ''T'' or ''τ'' is defined as the quotient between the sound intensity before and after the [[Phase Boundary Surface|interface]] ('''Eq. 1'''). It is therefore a [[Material Parameter|parameter]] for the transmitted intensity I and lies in the range between 0 and 1.

{|
|-
|width="20px"|
|width="500px"|<math>\tau = \frac{I}{I_{1}}</math>
|(1)
|}

The transmission degree of acoustic waves depends significantly on the thickness ''d'' of the test piece, the wavelength ''λ'' and the frequency ''f'', so that '''Eq. (2)''' actually applies. The frequency-dependent relationship is used, for example, in building acoustics to describe the acoustic insulation capacity of [[Plastic Component|components]], for which the logarithmic sound insulation index ''R'' is used ('''Eq. 3''').

{|
|-
|width="20px"|
|width="500px"|''τ'' = ''τ''(''λ'') or ''τ''(''f'')
|(2)
|}

{|
|-
|width="20px"|
|width="500px"|<math>R=10 \lg \left ( \frac{I_{0}}{I} \right )</math>
|(3)
|}

Analogous to the reflection factor ''R'', a transmission factor ''T'' can be specified for sound waves, which indicates how large the transmitted or passed portion ''P''D is ('''Fig. 1a'''), whereby this parameter refers to the amplitude of the sound waves rather than their intensity. This parameter ''D'' or ''T'' is also significantly dependent on the difference between the sound impedances ''W''1 and ''W''2 ('''Eq. 4''') [5, 7].

{|
|-
|width="20px"|
|width="500px"|<math>T=\frac{2 W_{2}}{W_{1}+W_{2}}</math>
|(4)
|}

When longitudinal waves are transmitted using vertical sensors, a high part of the sound waves is transmitted at the interface between the [[Ultrasonic Sensors|sensor]] and the test piece if the [[Surface|surface]] is very smooth and flat and a suitable coupling agent (water, coupling gel) is used ('''Fig. 1b'''). In the case of the [[Ultrasonic Immersion Bath Technique|immersion bath]] and [[Squirter Technique|squirter techniques]] or when using [[Air-Ultrasound|air-ultrasound]], the coupling problem does not occur. When sound waves are incident perpendicular to flat interfaces, no wave conversion occurs and, for identical media (''W''1 = ''W''2), ''R'' = 0 and ''T'' or ''D'' = 1, i.e. there is unimpeded sound transmission into medium 2. If there is no [[Absorption Sound Waves|absorption]] in the medium, the intensity or amplitude of the incident wave is identical to that of the outgoing sound wave.

[[File:Reflection Sound-2.jpg]]
{|
|- valign="top"
|width="50px"|'''Fig. 2''':
|width="600px"|[[Reflection Sound Waves|Reflection]] and transmission at the interface between two media a) and between [[Ultrasonic Sensors|ultrasonic sensor]] and specimen surface b) with oblique sound incidence [7]
|}

If the ultrasound enters the interface at an angle ('''Fig. 2'''), mode conversion or wave conversion, [[Reflection Sound Waves|reflection]], transmission and [[Refraction Sound Waves|refraction]] will occur in conjunction with frequency dispersion. Mode conversion is very important for some ultrasonic testing techniques, such as [[Ultrasonic Angle Beam Sensors|ultrasonic angle beam sensors]]. In this case, a transverse wave is additionally generated for both the reflected and transmitted waves. In the case of the angle sensor, depending on the difference in acoustic impedances and the angle of incidence, the longitudinal wave is totally reflected in medium 2 and the reflected transverse and longitudinal waves are attenuated in the sensor by an intermediate layer. In this case, the transmission factor ''T'' is calculated according to '''Eq. (5)''' as

{|
|-
|width="20px"|
|width="500px"|<math>T=\frac{P_{D}}{P_{0}}</math> with <math>T=R+1</math>.
|(5)
|}

==Application in defectoscopy==

In ultrasonic defectoscopy, defects or discontinuities in the [[Material & Werkstoff|material]] are more easily detectable the greater the differences in sound waves (echo detectability) are (e.g. steel − air: ''R'' >> - 1). Thin layers of air can prevent the transmission of sound waves into the material even with plane-parallel air gaps of 10 nm between the test head (steel) and a rough [[Surface|surface]] (air) at a test frequency of 1 MHz due to the large differences in ''W''. In transmission testing, the detection of [[Errors|defects]] (voids, inclusions, delaminations, doublings or [[Crack|cracks]]) or discontinuities is based on the transmission of the pulsed or continuous transmission pulse to the receiver sensor, therefore a transmitter and receiver sensor are always required. The measured amplitude pattern indicates the presence of defects and their spatial extent. The [[Ultrasonic Transmission Technique|ultrasonic transmission technique]] can be used in [[Ultrasonic Standard Sensors|standard]], [[Ultrasonic Transmitter(S)-Receiver(E) Sensor|transmitter (S)-receiver (E) sensor]] and [[Ultrasonic Angle Beam Sensors|angle testing techniques]].

[[File:Transmission_Sound-1.jpg]]
{|
|- valign="top"
|width="50px"|'''Fig. 3''':
|width="600px"|Ultrasonic transmission testing method on a test piece with a defect at a perpendicular sound incidence angle [7]
|}

==See also==

* [[Transmission Light|Transmission light]]
* [[Non-desdructive Polymer Testing|Non-desdructive polymer testing]]
* [[Velocity]]
* [[Ultrasonic Direct Coupling|Ultrasonic direct coupling]]
* [[Ultrasonic Birefrigence|Ultrasonic birefrigence]]

'''References'''

{|
|-valign="top"
|[1]
|Krautkrämer, J., Krautkrämer, H.: Ultrasonic Testing of Materials. Springer, Berlin (1990) 4th Edition, (ISBN 978-3-540-51231-8)
|-valign="top"
|[2]
|Lerch, R., Sessler, G., Wolf, D.: Technische Akustik – Grundlagen und Anwendung. Springer, Berlin (2009) (ISBN 978-3-540-49833-9)
|-valign="top"
|[3]
|Möser, M.: Technische Akustik. Springer, Berlin (2015) (ISBN 978-3-662-47704-5)
|-valign="top"
|[4]
|Šutilov, V. A.: Physik des Ultraschalls. Springer, Berlin (2013) (ISBN 978-3-70918-750-0) S. 155 ff.
|-valign="top"
|[5]
|Deutsch, V., Platte, M., Vogt, M.: Ultraschallprüfung. Grundlagen und industrielle Anwendungen. Springer, Berlin (2013) p. 33 (ISBN 978-3-642-63864-0)
|-valign="top"
|[6]
|Busse, G.: Non-desdructive Polymer Testing. In: [[Grellmann, Wolfgang|Grellmann, W.]], [[Seidler, Sabine|Seidler, S.]] (Eds.): Polymer Testing. Carl Hanser, Munich (2022) 3rd Edition, pp. 431–495 (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-805-5; see [[AMK-Büchersammlung|AMK-Library]] under A 22)
|-valign="top"
|[7]
|[[Bierögel, Christian|Bierögel, C.]]: Lecture Notes: Materials Diagnostics – Hybrid Testing Methods. Vienna University of Technology (2015)
|}

[[Category:Acoustic Test Methods_Ultrasonics]]

Transmission Sound Waves - Revision history

Oluschinski at 13:27, 12 December 2025