Calculator Inputs
Use the form below to estimate how much sound energy reflects and transmits when a wave passes from one medium into another.
Example Data Table
These sample values show how transmission changes when medium impedance changes significantly.
| Case | Medium 1 | Medium 2 | Frequency (Hz) | Transmission Ratio | Transmission Loss (dB) | Comment |
|---|---|---|---|---|---|---|
| 1 | Air | Glass | 1000 | 0.000337 | 34.72 | Large impedance mismatch produces strong reflection. |
| 2 | Water | Soft Tissue | 2000 | 0.999319 | 0.00 | Closely matched media transmit energy efficiently. |
| 3 | Air | Foam | 500 | 0.128104 | 8.92 | Moderate mismatch gives partial transfer and damping. |
Formula Used
Z = ρ × c
r = (Z2 - Z1) / (Z2 + Z1)
t = 2Z2 / (Z1 + Z2)
τ = 4Z1Z2 / (Z1 + Z2)2
R = ((Z2 - Z1) / (Z1 + Z2))2
TL = -10 log10(τ)
P = I × A and E = P × t
These equations assume normal-incidence plane waves and idealized lossless interfaces. For multilayer walls, porous absorbers, angled incidence, or structural vibration effects, a more detailed model is needed.
How to Use This Calculator
- Enter names for the two media so results remain easy to read.
- Provide density and sound speed for both sides of the interface.
- Enter the operating frequency to calculate wavelength and period.
- Choose either incident SPL or direct incident intensity input mode.
- Fill in area, exposure duration, and path length in the second medium.
- Click the calculate button to show results above the form.
- Review transmission loss, ratios, pressures, powers, and energy flow.
- Use the CSV or PDF buttons to save the result summary.
Frequently Asked Questions
1. What does sound transmission mean here?
It describes how much sound energy crosses from one medium into another at a boundary. Some energy reflects back, while the rest continues forward into the second material.
2. Why is acoustic impedance important?
Acoustic impedance combines density and sound speed. When two media have very different impedances, reflection increases and transmitted energy usually drops sharply.
3. What is transmission loss?
Transmission loss is the reduction in transmitted sound intensity, expressed in decibels. A higher value means less sound passes through the interface.
4. Is this calculator suitable for walls and full building assemblies?
It is best for single-interface wave transmission estimates. Real walls often need layered models, damping terms, coincidence effects, and structural coupling for accurate prediction.
5. Why can transmitted intensity stay low even with strong incident sound?
A severe impedance mismatch reflects most energy at the boundary. This happens often when sound moves from air into dense solids such as glass or steel.
6. What is the difference between SPL and intensity input?
SPL starts from pressure level in decibels. Intensity uses energy flow directly in watts per square meter. The calculator converts both into comparable transmission outputs.
7. Does frequency affect every result?
In this ideal boundary model, frequency mainly changes wavelength and period. More advanced real-world transmission models also make transmission strongly frequency dependent.
8. When should I use a more advanced acoustic model?
Use a more advanced model for layered barriers, oblique angles, porous treatments, resonance, room effects, vibration transfer, or standards-based construction acoustics analysis.