Moving from mini-SORAPS to the full SORAPS software can be motivated by several advanced features and capabilities that SORAPS offers, which are crucial for more complex and realistic simulations in underwater acoustics. Here are the reasons to transition to SORAPS:

1. 4D Propagation (3D + Time):

   • Reason: While mini-SORAPS is limited to 1D simulations with a constant sound speed, SORAPS provides 4D propagation modeling, which includes three spatial dimensions plus time. This capability is essential for accurately simulating real-world scenarios where acoustic waves propagate in a complex, dynamic environment. The additional dimensions allow for more precise modeling of how sound travels and interacts with the environment over time, providing a more comprehensive understanding of acoustic behavior.

2. 3D World Wide Database Integration (Geographic, Meteorologic, Oceanographic, Hydrographic):

   • Reason: SORAPS can incorporate detailed 3D databases that include geographic, meteorological, oceanographic, and hydrographic data. This integration allows for simulations that account for varying environmental conditions, such as changes in water temperature, salinity, and currents, which affect sound speed and propagation. Unlike the constant sound speed assumption in mini-SORAPS, this feature enables more accurate and realistic modeling of underwater acoustic environments.

3. Injection of Noise Measurement:

   • Reason: SORAPS allows for the injection of measured noise data, including reverberation, ambient noise levels, and antenna directivity patterns. This feature is crucial for realistic simulations as it accounts for actual noise conditions measured in the field, rather than relying solely on computational estimates. By incorporating real-world noise data, SORAPS can provide more accurate predictions of sonar performance and detection capabilities in varied and complex acoustic environments.

In summary, transitioning to SORAPS from mini-SORAPS is beneficial for users who require advanced simulation capabilities, including 4D propagation, integration with comprehensive environmental databases, and the ability to inject real-world noise measurements. These features make SORAPS a powerful tool for detailed and realistic underwater acoustic modeling and analysis.

SONAR EQUATIONS

mini-SORAPS, as a lightweight version of the SORAPS software, is designed to simulate acoustic wave propagation in a simplified marine environment. This tool can be particularly useful in understanding and applying concepts related to detection theory and the sonar equation, details below. 

Here's how they are linked:

1. Sonar Equation:

   • The sonar equation is a fundamental tool used to predict the performance of sonar systems. It typically considers factors such as source level, transmission loss, noise level, and detection threshold. By simulating acoustic propagation, mini-SORAPS can help estimate parameters like transmission loss, which is a key component of the sonar equation. This allows users to predict how changes in the environment or system setup might affect sonar performance.

2. Detection Theory:

   • Detection theory is concerned with how well a sonar system can detect signals in the presence of noise. It involves setting detection thresholds and understanding probabilities of detection and false alarms. By using mini-SORAPS to simulate different underwater acoustic scenarios, users can explore how changes in signal strength, noise levels, and environmental conditions impact detection capabilities. This can provide insights into optimizing detection thresholds and improving the overall effectiveness of sonar systems.

In summary, mini-SORAPS provides a practical tool for simulating underwater acoustic environments, which can be used to explore and understand the principles of the sonar equation and detection theory. 

This helps in predicting sonar performance and optimizing detection processes in various underwater scenarios.

Passive Sonar Case

In passive sonar, the system listens for sounds emitted by the target without transmitting any signal. The equation is:

ES = SL − TL − N + GT - DT

Where:

• ES (Excess of Signal): This is the amount by which a detected signal level surpasses the detection threshold, indicating the strength of the signal above the decision criterion.

• SL (Source Level): This is the level of the sound emitted by the target. It represents the acoustic power of the sound source.

• TL (Transmission Loss): This accounts for the loss of sound intensity as it travels through the water. Transmission loss can be due to spreading loss, absorption, scattering, etc.

• N (Noise Level): This represents the background noise level in the environment, which can interfere with the detection of the target signal.

  • No: This is the spectral density level of the noise.

  • The term N=No+10⋅log10​(No) is a way to express the total noise level, considering the noise spectral density.

• GT (Gain of the Receiver Array): This term accounts for the processing gain of the sonar system.

  • B: Bandwidth of the receiver.

  • T: Integration time.

  • K: Number of post intégration.

  • The term GT=10⋅log⁡10(B⋅T)+5⋅log⁡10(K) represents the gain due to signal processing and array configuration.

• DT: The Detection Threshold (DT) is a set value used to determine the presence of a signal within observed data. 

Active Sonar Case

In active sonar, the system transmits a signal and listens for its echo from the target. The equation is:

ES = SL − TL − TS − TL − N + GT - DT

Where:

• ES (Excess of Signal): Similar to passive sonar, this is the amount by which a detected signal level surpasses the detection threshold after it has traveled to the target and back.

• SL (Source Level): This is the level of the sound transmitted by the sonar system.

• TL (Transmission Loss): This term appears twice because the sound travels from the sonar to the target and back to the sonar.

• TS (Target Strength): This represents the reflective strength of the target. It accounts for how much sound is reflected back towards the sonar system.

• N (Noise Level): Similar to passive sonar, this represents the background noise level.

  • No: Spectral density level of the noise.

  • The term N=No+10⋅log⁡10(No) is used to express the total noise level.

• GT (Gain of the Receiver Array): This term is the same as in passive sonar and accounts for the processing gain of the sonar system.

  • B: Bandwidth of the receiver.

  • T: Integration time.

  • K: Number of post intégration.

  • The term GT=10⋅log⁡10(B⋅T)+5⋅log⁡10(K) represents the gain due to signal processing and array configuration.

• DT: The Detection Threshold (DT) is a set value used to determine the presence of a signal within observed data. 

These equations and terms are fundamental in understanding how sonar systems detect and interpret sounds in underwater environments.

In the context of sonar equations, the values are often expressed in decibels (dB), which is a logarithmic unit used to describe the ratio of a measured value to a reference value. Here's how each term in the sonar equations relates to decibels:

• Source Level (SL):

  • Expressed in dB, it quantifies the strength of the sound emitted by the source (e.g., a ship or marine animal in passive sonar, or the sonar transmitter in active sonar). It is referenced to a standard distance, typically 1 meter.

• Transmission Loss (TL):

  • Also in dB, this term accounts for the reduction in sound intensity as it travels through the water. Transmission loss includes effects from spherical spreading, absorption by the water, and scattering.

• Noise Level (N):

  • Expressed in dB, this represents the ambient noise present in the environment, which can mask the signal of interest. It includes contributions from various sources such as waves, marine life, and distant shipping.

• Target Strength (TS):

  • Expressed in dB, TS is used in active sonar to describe how much sound is reflected by the target back towards the sonar receiver. It is a measure of the target's ability to reflect sound.

• Excess of Signal (ES):

  • Expressed in dB, Excess of Signal (ES) is the difference between the measured level of a signal and the predefined detection threshold. If the signal level surpasses this threshold, it indicates the presence of a meaningful signal rather than just noise. ES is crucial because it provides a quantitative measure of how much stronger the signal is compared to the threshold level. A higher ES generally implies a more robust detection, reducing the likelihood of false alarms and increasing confidence in the detection of actual signals. In practical applications, understanding and optimizing ES helps in fine-tuning detection systems to improve their sensitivity and reliability, ensuring that true signals are detected with higher accuracy while minimizing the chances of false detections.

• Gain of the Receiver Array (GT):

  • Expressed in dB, GT accounts for the processing gain achieved by the sonar system, which can enhance the signal relative to the noise. This includes gains from signal processing techniques and the use of multiple array elements.

• Detection Threshold (DT):

  • Expressed in dB, The Detection Threshold (DT) is a set value used to determine the presence of a signal within observed data. It balances the trade-off between correctly identifying actual signals and minimizing false alarms. By adjusting this threshold, the sensitivity and accuracy of signal detection can be optimized.

The use of decibels allows for convenient representation and manipulation of values that can span several orders of magnitude, which is typical in acoustics and signal processing. The logarithmic nature of the decibel scale also aligns well with human perception of sound intensity.

DETECTIONS