Mathematics · Mathematical Physics
Acoustic Directivity Index Calculator
Calculate directivity index in decibels from sound-source directivity factor and isotropic reference factor.
Inputs and results stay in this browser. Change one value at a time to explore the relationship.
Calculation steps
- Use c=10log₁₀(a/b) with sound-source directivity factor=4 and isotropic reference factor=1.
- directivity index in decibels=6.020599913279623.
Understand Acoustic Directivity Index
One idea, three depths
Choose how deeply to explain Acoustic Directivity Index
Acoustic Directivity Index: Calculate directivity index in decibels from sound-source directivity factor and isotropic reference factor.
Age 5Explain it to a 5-year-oldStart with a picture
Imagine using Acoustic Directivity Index to answer this question: calculate directivity index in decibels from sound-source directivity factor and isotropic reference factor? Enter sound-source directivity factor and isotropic reference factor; the calculator shows directivity index in decibels. For example: sound-source directivity factor=4 and isotropic reference factor=1 produce directivity index in decibels=6.020599913279623. The answer tells you directivity index in decibels.
Age 15Explain it to a 15-year-oldConnect it to the formula
Acoustic directivity index is ten times log base ten of directivity factor relative to the stated reference. This page evaluates the relationship directly. The rule is c=10log₁₀(a/b). Its input values are sound-source directivity factor, isotropic reference factor, and the main result is directivity index in decibels. For example: sound-source directivity factor=4 and isotropic reference factor=1 produce directivity index in decibels=6.020599913279623.
CollegeExplain it at college levelState the model precisely
This calculator evaluates the stated acoustic directivity index relation over the valid real-number domain stated below. The implemented relation is c=10log₁₀(a/b), evaluated from sound-source directivity factor, isotropic reference factor to produce directivity index in decibels. Acoustic directivity index is ten times log base ten of directivity factor relative to the stated reference. This page evaluates the relationship directly. Frequency, radiation plane, environment, source mounting, averaging, and whether intensity or power directivity is used must be specified.
Inputs and valid domain
- sound-source directivity factor must be a finite real number.
- isotropic reference factor must be a finite real number.
Important boundary: Frequency, radiation plane, environment, source mounting, averaging, and whether intensity or power directivity is used must be specified.
The formula
c=10log₁₀(a/b)
How the calculator works through it
It substitutes sound-source directivity factor, isotropic reference factor into the formula and exposes every numerical step above. The main output is directivity index in decibels.
Read the result correctly
The directivity index in decibels is the direct answer to “calculate directivity index in decibels from sound-source directivity factor and isotropic reference factor.” Read it with the units shown beside the inputs; a sign, angle, percentage or rate changes what the number means.
A worked check
sound-source directivity factor=4 and isotropic reference factor=1 produce directivity index in decibels=6.020599913279623.
Where this model stops being reliable
Frequency, radiation plane, environment, source mounting, averaging, and whether intensity or power directivity is used must be specified.
Learn it by changing one value
Begin with the worked example, then change one value while keeping the others fixed. Compare the new result and calculation steps to identify which part of the formula changed.
Dictionary terms behind this calculator
Before studying the codeWhat you should know firstUse the calculator immediately, or check the foundations before reading the implementation.
These foundations help you understand why Acoustic Directivity Index works. They never block the calculator, and “optional” means useful context rather than a hidden requirement.
Hard requirements
- Reading formulas and substituting values
Acoustic Directivity Index uses c=10log₁₀(a/b). You need to recognise what each side represents before substituting the stated inputs or rearranging the relationship.
Review this foundation about 4 min
Strong support
- Ratios, units and dimensional meaning
Tracking ratios and units keeps the Acoustic Directivity Index result physically interpretable instead of merely numerical.
Review this foundation about 5 min
Optional enrichment
- Vectors and physical direction
Vector language extends Acoustic Directivity Index when magnitude and direction must be treated separately.
Review this foundation about 6 min
Mathematics → algorithm → program
Implement this calculation in code
These are direct reference implementations of the calculator's principal relationship and first output. They run locally and include a small known-answer check where the language supports it.
Algorithm
- Read sound-source directivity factor, isotropic reference factor.
- Evaluate the principal relationship: c=10log₁₀(a/b).
- Return directivity index in decibels and check the domain conditions described above.
Python
from math import *
def acoustic_directivity_index_calculator(a, b) -> float:
return ((10.0 * log((a / b))) / log(10.0))
assert abs(acoustic_directivity_index_calculator(4, 1) - 6.020599913279623) < 1e-6 * max(1.0, abs(6.020599913279623))
C
#include <assert.h>
#include <math.h>
double acoustic_directivity_index_calculator(double a, double b) {
return ((10.0 * log((a / b))) / log(10.0));
}
int main(void) {
const double expected = 6.020599913279623;
const double actual = acoustic_directivity_index_calculator(4, 1);
assert(fabs(actual - expected) < 1e-6 * fmax(1.0, fabs(expected)));
}
C++
#include <cassert>
#include <cmath>
#include <numbers>
double acoustic_directivity_index_calculator(double a, double b) {
return ((10.0 * std::log((a / b))) / std::log(10.0));
}
int main() {
constexpr double expected = 6.020599913279623;
const double actual = acoustic_directivity_index_calculator(4, 1);
assert(std::fabs(actual - expected) < 1e-6 * std::fmax(1.0, std::fabs(expected)));
}
Linux x86-64 assembly
x86-64 NASM · System V ABI · Linux · SSE2 with libm where required
; double acoustic_directivity_index_calculator(double a, double b)
; Linux x86-64 NASM · System V ABI · first eight doubles in xmm0–xmm7
extern log
global acoustic_directivity_index_calculator
section .text
acoustic_directivity_index_calculator:
push rbp
mov rbp, rsp
sub rsp, 80
movsd [rbp-8], xmm0
movsd [rbp-16], xmm1
mov rax, 0x4024000000000000
movq xmm0, rax
movsd [rbp-40], xmm0
movsd xmm0, [rbp-8]
divsd xmm0, [rbp-16]
movsd [rbp-56], xmm0
movsd xmm0, [rbp-56]
call log wrt ..plt
movsd [rbp-48], xmm0
movsd xmm0, [rbp-40]
mulsd xmm0, [rbp-48]
movsd [rbp-32], xmm0
mov rax, 0x4024000000000000
movq xmm0, rax
movsd [rbp-72], xmm0
movsd xmm0, [rbp-72]
call log wrt ..plt
movsd [rbp-64], xmm0
movsd xmm0, [rbp-32]
divsd xmm0, [rbp-64]
movsd [rbp-24], xmm0
movsd xmm0, [rbp-24]
leave
ret
MATLAB
function result = acoustic_directivity_index_calculator(a, b)
result = ((10.0 * log((a / b))) / log(10.0));
end
Wolfram Language
ClearAll[mwCalculate];
mwCalculate[a_, b_] := ((10.0 * Log[(a / b)]) / Log[10.0]);
Continue in mathematical software
The downloaded file includes your current inputs and first calculated result. It is created locally.
Floating-point answers can differ slightly by language, compiler and processor. Compare within a suitable tolerance rather than assuming every decimal representation will be identical.
Supporting sourcesAcademic referencesPrimary standards, textbooks and complete citations
Standards, reading and academic references
Use the calculator as the worked interaction, then consult the primary standards and academic textbooks listed below. MW SysArc links to the original sources; the explanation on this page is original and does not reproduce them.
University Physics Volume 3
Read OpenStax University Physics: Quantum MechanicsCite this book
- APA 7
- Ling, S. J., Sanny, J., & Moebs, W. (2016). University physics volume 3. OpenStax. https://openstax.org/books/university-physics-volume-3/pages/1-introduction
- MLA 9
- Ling, Samuel J., et al. University Physics Volume 3. OpenStax, 2016, https://openstax.org/books/university-physics-volume-3/pages/1-introduction.
- Chicago author-date
- Ling, Samuel J., Jeff Sanny, and William Moebs. 2016. University Physics Volume 3. Houston, TX: OpenStax. https://openstax.org/books/university-physics-volume-3/pages/1-introduction.
OpenStax entries are free to read online. Follow the licence shown on each linked source before redistributing or adapting its content.
Reuse the page responsiblyCite this pageAPA, MLA, Chicago, Harvard, BibTeX and RIS
These formats cite this calculator page itself. They are separate from the academic references above, which support the mathematical method and terminology.
APA 7
MW SysArc. (2026, July 21). Acoustic Directivity Index Calculator. MW SysArc Tools. https://math.mwsysarc.com/mathematical-physics/acoustic-directivity-index-calculator
MLA 9
MW SysArc. “Acoustic Directivity Index Calculator.” MW SysArc Tools, 21 July 2026, https://math.mwsysarc.com/mathematical-physics/acoustic-directivity-index-calculator. Accessed 31 Aug. 2026.
Chicago 17
MW SysArc. “Acoustic Directivity Index Calculator.” MW SysArc Tools. Published July 21, 2026. Accessed August 31, 2026. https://math.mwsysarc.com/mathematical-physics/acoustic-directivity-index-calculator.
Harvard
MW SysArc (2026) ‘Acoustic Directivity Index Calculator’, MW SysArc Tools. Published 21 July 2026. Available at: https://math.mwsysarc.com/mathematical-physics/acoustic-directivity-index-calculator (Accessed: 31 August 2026).
BibTeX and RIS records
BibTeX
@misc{mwsysarc_acoustic_directivity_index_calculator_2026,
author = {{MW SysArc}},
title = {Acoustic Directivity Index Calculator},
howpublished = {MW SysArc Tools},
year = {2026},
url = {https://math.mwsysarc.com/mathematical-physics/acoustic-directivity-index-calculator},
note = {Published July 21, 2026; accessed August 31, 2026}
}RIS
TY - ELEC
AU - MW SysArc
TI - Acoustic Directivity Index Calculator
T2 - MW SysArc Tools
PY - 2026
DA - 2026-07-21
Y2 - 2026-08-31
UR - https://math.mwsysarc.com/mathematical-physics/acoustic-directivity-index-calculator
N1 - Published July 21, 2026
ER -Clear answers
Frequently asked questions
What does the Acoustic Directivity Index do?
Calculate directivity index in decibels from sound-source directivity factor and isotropic reference factor.
How does the Acoustic Directivity Index work?
The calculator applies c=10log₁₀(a/b). Acoustic directivity index is ten times log base ten of directivity factor relative to the stated reference. This page evaluates the relationship directly.
What can I learn from the Acoustic Directivity Index?
It connects the mathematical rule to your chosen numbers and shows each calculation step. Change one input at a time to see how the result responds.
Does MW SysArc receive or store what I enter?
No. The calculation runs locally in your browser. MW SysArc does not receive or store your calculation inputs.
How should I use the result?
Use the steps to understand the method, then verify important school or professional work using the notation and rounding rules required in your setting.
Last reviewed . Calculations tested .