View source for Waveform analysis/Doh ray me

{{draft task}}
Analyse a given section of monophonic audio waveform, for average pitch and output one of the sol-fa trigraphs (like [[wp:Tonic_sol-fa|these]], except each has three letters) corresponding to average pitch level: Doh, Ray, Mee, Fah, Soh, Lah, Tee, doh.

Optionally, follow the trigraph with a plus or minus symbol, to indicate whether the note falls above or below the solfa. Extend the scale to cover 21 notes: DOH, RAY, MEE, FAH, SOH, LAH, TEE, Doh, Ray, Mee, Fah, Soh, Lah, Tee, doh, ray, mee, fah, soh, lah, tee.

A calibration parameter can be provided to suit different voices. This can be provided as a variable defined within the code.

=={{header|Go}}==
Clearly, this task is only feasible if you know how frequencies are encoded as bytes in the waveform and even then there are mathematical difficulties in reversing the procedure which mean that the eventual result is unlikely to be exact.

As an example, we analyze the .wav file (notes.wav) created by the [[https://rosettacode.org/wiki/Musical_scale#Go Musical Scale]] task. As we know that the same frequency was used to generate each sample (44100 bytes), it is only necessary to examine a small number of bytes for each sample to determine the average frequency for the file as a whole (8 samples). 

However, as each calculation was of necessity rounded to the nearer byte, it seems sensible to use more than one byte per sample (but not so many that the multi-valued arcsine function will be applied to a value outside its principal range) to try and reduce the effect of rounding. 20 bytes per sample is used here though curiously using only 3 bytes per sample would have produced a more accurate result (384.9 Hz).

Some optional aspects of the task have been ignored as they are not relevant to this particular example.
<syntaxhighlight lang="go">package main

import (
    "encoding/binary"
    "fmt"
    "log"
    "math"
    "os"
)

var (
    freqs = []float64{261.6, 293.6, 329.6, 349.2, 392.0, 440.0, 493.9, 523.3}
    notes = []string{"Doh", "Ray", "Mee", "Fah", "Soh", "Lah", "Tee", "doh"}
)

func getNote(freq float64) string {
    index := len(freqs)
    for i := 0; i < len(freqs); i++ {
        if freq <= freqs[i] {
            index = i
            break
        }
    }
    switch index {
    case 0:
        return "Doh-"
    case len(freqs):
        return "doh+"
    default:
        if freqs[index]-freq <= freq-freqs[index-1] {
            return notes[index] + "-"
        }
        return notes[index-1] + "+"
    }
}

func check(err error) {
    if err != nil {
        log.Fatal(err)
    }
}

func main() {
    file, err := os.Open("notes.wav")
    check(err)
    defer file.Close()    
    hdr := make([]byte, 44)
    _, err = file.Read(hdr)
    check(err)
    // check header parameters
    sampleRate := int(binary.LittleEndian.Uint32(hdr[24:28]))
    fmt.Println("Sample Rate    :", sampleRate)
    dataLength := int(binary.LittleEndian.Uint32(hdr[40:]))
    duration := dataLength / sampleRate
    fmt.Println("Duration       :", duration)

    sum := 0.0
    sampleRateF := float64(sampleRate)
    data := make([]byte, sampleRate)
    nbytes := 20
    fmt.Println("Bytes examined :", nbytes, "per sample") 
    for j := 0; j < duration; j++ {
        _, err := file.Read(data)
        check(err)
        for i := 1; i <= nbytes; i++ {
            bf := float64(data[i]) / 32
            freq := math.Asin(bf) * sampleRateF / (float64(i) * math.Pi * 2)
            sum += freq
        }
    }
    cav := sum / (float64(duration) * float64(nbytes))
    fmt.Printf("\nComputed average frequency = %.1f Hz (%s)\n", cav, getNote(cav))

    sum = 0.0
    for i := 0; i < len(freqs); i++ {
        sum += freqs[i]
    }
    aav := sum / float64(len(freqs))
    fmt.Printf("Actual average frequency   = %.1f Hz (%s)\n", aav, getNote(aav))
}</syntaxhighlight>

{{out}}
<pre>
Sample Rate    : 44100
Duration       : 8
Bytes examined : 20 per sample

Computed average frequency = 387.1 Hz (Soh-)
Actual average frequency   = 385.4 Hz (Soh-)</pre>

=={{header|Julia}}==
Uses the LibSndFile library for WAV file reading and the DSP module's implementation of the ESPRIT algorithm to analyze the sound for its fundamental frequency.
<syntaxhighlight lang="julia">using DSP, FileIO, LibSndFile

const soundfilename = "Cscale3octaves.wav"
const freq_to_solfa = Dict([
130.81 => "DOH"
146.83 => "RAY"
164.81 => "MEE"
174.61 => "FAH"
196.0 => "SOH"
220.0 => "LAH"
246.94 => "TEE"
261.63 => "Doh"
293.66 => "Ray"
329.63 => "Mee"
349.23 => "Fah"
392.0 => "Soh"
440.0 => "Lah"
493.88 => "Tee"
523.25 => "doh"
587.33 => "ray"
659.25 => "mee"
698.46 => "fah"
783.99 => "soh"
880.0 => "lah"
987.77 => "tee"
])
const sfreqs = sort(collect(keys(freq_to_solfa)))

function closestfreqs(samples, fs=44100.0)
    pfreqs = Float64[]
    for sample in samples
        M = div(length(sample) + 1, 3)
        arr = [Complex{Float64}(x) for x in sample]
        narr = filter(x -> x > 0, esprit(arr, M, 4, fs))
        idx = argmin([abs(f - narr[end]) for f in sfreqs])
        push!(pfreqs, sfreqs[idx])
    end
    return pfreqs
end

function getchunks(soundfile, channel=1, timespan=0.1)
    sv = load(soundfile)
    fs = LibSndFile.samplerate(sv)
    samplespan, data = Int(round(timespan * fs)), view(sv, :, channel)
    return (fs, [data[i:i+samplespan-1] for i in 1:samplespan:length(data)-samplespan-1])
end

function makenotelist(soundfile, repetitionsneeded=2)
    changelist = String[]
    fs, samples = getchunks(soundfile)
    freqs = closestfreqs(samples, fs)
    reps, prev = 0, ""
    for freq in freqs
        note = freq_to_solfa[freq]
        if note != prev
            prev = note
            reps = 0
        else
            reps += 1
            if reps == repetitionsneeded
               push!(changelist, note)
            end
        end
    end
    return changelist
end

println(makenotelist(soundfilename))

</syntaxhighlight>{{out}}
<pre>
["DOH", "RAY", "MEE", "FAH", "SOH", "LAH", "TEE", "Doh", "Ray", "Mee", "Fah", "Soh", "Lah", "Lah", "Tee", "doh", "ray", "mee", "fah", "soh", "lah", "tee"]
</pre>

=={{header|Nim}}==
{{trans|Go}}
The input .wav file (notes.wav) is created by the [[https://rosettacode.org/wiki/Musical_scale#Nim Musical Scale#Nim]] entry.

<syntaxhighlight lang="nim">import endians, math, stats, strformat

const
  Freqs = [261.6, 293.6, 329.6, 349.2, 392.0, 440.0, 493.9, 523.3]
  Notes = ["Doh", "Ray", "Mee", "Fah", "Soh", "Lah", "Tee", "doh"]


func getNote(freq: float): string =
  var index = Freqs.len
  for i, f in Freqs:
    if freq <= f:
      index = i
      break
  result = if index == 0:
             "Doh-"
           elif index == Freqs.len:
             "doh+"
           elif Freqs[index] - freq <= freq - Freqs[index-1]:
             Notes[index] & '-'
           else:
             Notes[index-1] & '+'


proc getUint32(buffer: openArray[byte]; pos: Natural): uint32 =
  littleEndian32(result.addr, buffer[pos].unsafeAddr)


let file = open("notes.wav")
var hdr: array[44, byte]
let n = file.readBytes(hdr, 0, hdr.len)
doAssert n == hdr.len

# Check header parameters.
let sampleRate = hdr.getUint32(24)
echo "Sample rate:    ", sampleRate
let dataLength = hdr.getUint32(40)
let duration = dataLength div sampleRate
echo "Duration:       ", duration

var sum = 0.0
let sampleRateF = float(sampleRate)
var data = newSeq[byte](sampleRate)
let nbytes = 20
echo "Bytes examined: ", nbytes, " per sample"
for j in 0..<duration:
  let n = file.readBytes(data, 0, data.len)
  doAssert n == data.len
  for i in 1..nbytes:
    let bf = float(data[i]) / 32
    let freq = arcsin(bf) * sampleRateF / (i.toFloat * 2 * Pi)
    sum += freq
let cav = sum / float(duration.int * nbytes)
echo &"\nComputed average frequency = {cav:.1f} Hz ({cav.getNote()})"

let aav = mean(Freqs)
echo &"Actual average frequency   = {aav:.1f} Hz ({aav.getNote()})"</syntaxhighlight>

{{out}}
<pre>Sample rate:    44100
Duration:       8
Bytes examined: 20 per sample

Computed average frequency = 387.1 Hz (Soh-)
Actual average frequency   = 385.4 Hz (Soh-)</pre>

file.close()

=={{header|Perl}}==
The input .wav file (notes.wav) is created by the [[https://rosettacode.org/wiki/Musical_scale#Go Musical Scale#Go]] entry.
{{trans|Raku}}
<syntaxhighlight lang="perl"># 20200808 added Perl programming solution

use v5.10;
use strict;
use warnings;
use autodie;

use Math::Trig;
use List::Util qw/sum/;
use constant PI => 4 * atan2(1, 1);

my @freqs = qw ( 261.6 293.6 329.6 349.2 392.0 440.0 493.9 523.3 );
my @notes = qw ( Doh Ray Mee Fah Soh Lah Tee doh );

sub getNote {
   my $freq  = $_[0];
   my $index = @freqs;
   for (0..$index-1) { $index = $_ and last if $freq <= $freqs[$_] }
   given ($index) {
      when (0)      { "Doh-" }
      when (@freqs) { "doh+" }
      default       { $freqs[$index] - $freq <= $freq - $freqs[$index-1]
                         ? $notes[$index] . "-" : $notes[$index-1] . "+" }
   }
}


open my $fh, '<:raw', './notes.wav';

# http://www.topherlee.com/software/pcm-tut-wavformat.html

read $fh, my $header, 28;
print "Sample Rate    : ", my $sampleRate = unpack(' x24 L< ', $header), "\n" ;

read $fh, $header, 16;
my $dataLength = unpack(' x12 L< ', $header);
print "Duration       : ", my $duration = $dataLength / $sampleRate, "\n";

my ( $sum, $nbytes )  =  ( 0, 20 ) ;

print "Bytes examined : $nbytes per sample\n";

while ( read $fh, my $data, $sampleRate ) {
   my @chunk = split('', $data);
   for my $k (1..$nbytes) {
      my $bf = ord($chunk[$k]) / 32;
      $sum += asin($bf) * $sampleRate / ( 2 * PI * $k );
   }
}

close $fh;

my $cav = $sum / ( $duration * $nbytes );
printf "Computed average frequency = %.1f", $cav;
print  " Hz (",getNote($cav),")\n";

my $aav = sum(@freqs) / @freqs;
printf "Actual   average frequency = %.1f", $aav;
print  " Hz (",getNote($aav),")\n";
</syntaxhighlight>
{{out}}
<pre>go run Musical_scale.go
file notes.wav
notes.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 8 bit, mono 44100 Hz
./Doh_ray_me.pl
Sample Rate    : 44100
Duration       : 8
Bytes examined : 20 per sample
Computed average frequency = 387.1 Hz (Soh-)
Actual   average frequency = 385.4 Hz (Soh-)
</pre>

=={{header|Phix}}==
{{trans|Go}}
Likewise analyses the output file of [[Musical_scale#Phix]]
<!--<syntaxhighlight lang="phix">(notonline)-->
 <span style="color: #008080;">without</span> <span style="color: #008080;">js</span> <span style="color: #000080;font-style:italic;">-- (file i/o)</span>
 <span style="color: #008080;">constant</span> <span style="color: #000000;">freqs</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">261.6</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">293.6</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">329.6</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">349.2</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">392.0</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">440.0</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">493.9</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">523.3</span><span style="color: #0000FF;">},</span>
          <span style="color: #000000;">notes</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #008000;">"Doh"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"Ray"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"Mee"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"Fah"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"Soh"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"Lah"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"Tee"</span><span style="color: #0000FF;">,</span> <span style="color: #008000;">"doh"</span><span style="color: #0000FF;">}</span>
  
 <span style="color: #008080;">function</span> <span style="color: #000000;">getNote</span><span style="color: #0000FF;">(</span><span style="color: #004080;">atom</span> <span style="color: #000000;">freq</span><span style="color: #0000FF;">)</span>
     <span style="color: #004080;">integer</span> <span style="color: #000000;">idx</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">freqs</span><span style="color: #0000FF;">)+</span><span style="color: #000000;">1</span>
     <span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">freqs</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
         <span style="color: #008080;">if</span> <span style="color: #000000;">freq</span><span style="color: #0000FF;"><=</span><span style="color: #000000;">freqs</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]</span> <span style="color: #008080;">then</span>
             <span style="color: #000000;">idx</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">i</span>
             <span style="color: #008080;">exit</span>
         <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
     <span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
     <span style="color: #004080;">string</span> <span style="color: #000000;">res</span>
     <span style="color: #008080;">if</span> <span style="color: #000000;">idx</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">then</span>
         <span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span>  <span style="color: #008000;">"Doh-"</span>
     <span style="color: #008080;">elsif</span> <span style="color: #000000;">idx</span><span style="color: #0000FF;">></span><span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">freqs</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span>
         <span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #008000;">"doh+"</span>
     <span style="color: #008080;">elsif</span> <span style="color: #000000;">freqs</span><span style="color: #0000FF;">[</span><span style="color: #000000;">idx</span><span style="color: #0000FF;">]-</span><span style="color: #000000;">freq</span> <span style="color: #0000FF;"><=</span> <span style="color: #000000;">freq</span><span style="color: #0000FF;">-</span><span style="color: #000000;">freqs</span><span style="color: #0000FF;">[</span><span style="color: #000000;">idx</span><span style="color: #0000FF;">-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">]</span> <span style="color: #008080;">then</span>
         <span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">notes</span><span style="color: #0000FF;">[</span><span style="color: #000000;">idx</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">&</span> <span style="color: #008000;">"-"</span>
     <span style="color: #008080;">else</span>
         <span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">notes</span><span style="color: #0000FF;">[</span><span style="color: #000000;">idx</span><span style="color: #0000FF;">-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">&</span> <span style="color: #008000;">"+"</span>
     <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
     <span style="color: #008080;">return</span> <span style="color: #000000;">res</span>
 <span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
  
 <span style="color: #004080;">object</span> <span style="color: #000000;">data</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">get_text</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"notes.wav"</span><span style="color: #0000FF;">)</span>
 <span style="color: #008080;">if</span> <span style="color: #000000;">data</span><span style="color: #0000FF;">=-</span><span style="color: #000000;">1</span> <span style="color: #008080;">then</span> <span style="color: #7060A8;">crash</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"error opening notes.wav"</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
 <span style="color: #004080;">integer</span> <span style="color: #000000;">sampleRate</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">bytes_to_int</span><span style="color: #0000FF;">(</span><span style="color: #000000;">data</span><span style="color: #0000FF;">[</span><span style="color: #000000;">25</span><span style="color: #0000FF;">..</span><span style="color: #000000;">28</span><span style="color: #0000FF;">]),</span>
         <span style="color: #000000;">dataLength</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">bytes_to_int</span><span style="color: #0000FF;">(</span><span style="color: #000000;">data</span><span style="color: #0000FF;">[</span><span style="color: #000000;">41</span><span style="color: #0000FF;">..</span><span style="color: #000000;">44</span><span style="color: #0000FF;">]),</span>
         <span style="color: #000000;">nbytes</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">20</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">offset</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">45</span>
 <span style="color: #004080;">atom</span> <span style="color: #000000;">duration</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">dataLength</span><span style="color: #0000FF;">/</span><span style="color: #000000;">sampleRate</span><span style="color: #0000FF;">,</span>
      <span style="color: #000000;">tot</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
 <span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Sample Rate    : %d\n"</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">sampleRate</span><span style="color: #0000FF;">)</span>
 <span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Duration       : %s\n"</span><span style="color: #0000FF;">,</span> <span style="color: #7060A8;">elapsed</span><span style="color: #0000FF;">(</span><span style="color: #000000;">duration</span><span style="color: #0000FF;">))</span>
 <span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Bytes examined : %d per sample\n\n"</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">nbytes</span><span style="color: #0000FF;">)</span> 
 <span style="color: #008080;">for</span> <span style="color: #000000;">j</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #000000;">duration</span> <span style="color: #008080;">do</span>
     <span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #000000;">nbytes</span> <span style="color: #008080;">do</span>
         <span style="color: #004080;">atom</span> <span style="color: #000000;">bf</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">data</span><span style="color: #0000FF;">[</span><span style="color: #000000;">offset</span><span style="color: #0000FF;">+</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]/</span><span style="color: #000000;">32</span><span style="color: #0000FF;">,</span>
              <span style="color: #000000;">freq</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">arcsin</span><span style="color: #0000FF;">(</span><span style="color: #000000;">bf</span><span style="color: #0000FF;">)</span> <span style="color: #0000FF;">*</span> <span style="color: #000000;">sampleRate</span> <span style="color: #0000FF;">/</span> <span style="color: #0000FF;">(</span><span style="color: #000000;">i</span><span style="color: #0000FF;">*</span><span style="color: #004600;">PI</span><span style="color: #0000FF;">*</span><span style="color: #000000;">2</span><span style="color: #0000FF;">)</span>
         <span style="color: #000000;">tot</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">freq</span>
     <span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
     <span style="color: #000000;">offset</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">sampleRate</span>
 <span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
 <span style="color: #004080;">atom</span> <span style="color: #000000;">cav</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">tot</span> <span style="color: #0000FF;">/</span> <span style="color: #0000FF;">(</span><span style="color: #000000;">duration</span> <span style="color: #0000FF;">*</span> <span style="color: #000000;">nbytes</span><span style="color: #0000FF;">),</span>
      <span style="color: #000000;">aav</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">sum</span><span style="color: #0000FF;">(</span><span style="color: #000000;">freqs</span><span style="color: #0000FF;">)</span> <span style="color: #0000FF;">/</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">freqs</span><span style="color: #0000FF;">)</span>
 <span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Computed average frequency = %.1f Hz (%s)\n"</span><span style="color: #0000FF;">,</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">cav</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">getNote</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cav</span><span style="color: #0000FF;">)})</span>
 <span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"Actual average frequency   = %.1f Hz (%s)\n"</span><span style="color: #0000FF;">,</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">aav</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">getNote</span><span style="color: #0000FF;">(</span><span style="color: #000000;">aav</span><span style="color: #0000FF;">)})</span>
<!--</syntaxhighlight>-->
{{out}}
<pre>
Sample Rate    : 44100
Duration       : 8s
Bytes examined : 20 per sample

Computed average frequency = 387.1 Hz (Soh-)
Actual average frequency   = 385.4 Hz (Soh-)
</pre>

=={{header|Raku}}==
The input .wav file (notes.wav) is created by the [[https://rosettacode.org/wiki/Musical_scale#Go Musical Scale#Go]] entry.
{{trans|Go}}
<syntaxhighlight lang="raku" line># 20200721 Raku programming solution

my \freqs = < 261.6 293.6 329.6 349.2 392.0 440.0 493.9 523.3 >;
my \notes = < Doh Ray Mee Fah Soh Lah Tee doh >;

sub getNote (\freq) {
   my $index = freqs;
   for (0..^$index) { $index = $_ and last if freq ≤ freqs[$_] }
   given $index {
      when 0     { "Doh-" }
      when freqs { "doh+" }
      default    { freqs[$index] - freq ≤ freq - freqs[$index-1]
                       ?? notes[$index] ~ "-" !! notes[$index-1] ~ "+" }
   }
}

my $file = slurp "./notes.wav", :bin or die;

# http://www.topherlee.com/software/pcm-tut-wavformat.html
# https://stackoverflow.com/a/49081648/3386748

my $sampleRate = Blob.new(@$file[24..27]).read-uint32(0,LittleEndian);
# self-ref: [+] @$file[24..27].pairs.map: {$_.value*256**$_.key};
say "Sample Rate    : ", $sampleRate;

my $dataLength = Blob.new(@$file[40..43]).read-uint32(0,LittleEndian);
# self-ref: [+] @$file[40..43].pairs.map: {$_.value*256**$_.key};
my $duration = $dataLength / $sampleRate;
say "Duration       : ", $duration;

my ( $sum, $sampleRateF )  =  ( 0, $sampleRate.Num ) ;
my $nbytes = 20;

say "Bytes examined : ", $nbytes, " per sample";

for @$file[44..*].rotor($sampleRate) -> $data {
   for (1..$nbytes) -> $k {
      my $bf = @$data[$k] / 32;
      $sum += $bf.asin × $sampleRateF / ( 2 × π × $k );
   }
}

my $cav = $sum / ( $duration * $nbytes );
say "Computed average frequency = {$cav.fmt('%.1f')} Hz ({getNote($cav)})";

my $aav = ([+] freqs) / freqs;
say "Actual   average frequency = {$aav.fmt('%.1f')} Hz ({getNote($aav)})";</syntaxhighlight>
{{out}}
<pre>go run Musical_scale.go
file notes.wav
notes.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 8 bit, mono 44100 Hz
./Doh_ray_me.raku
Sample Rate    : 44100
Duration       : 8
Bytes examined : 20 per sample
Computed average frequency = 387.1 Hz (Soh-)
Actual   average frequency = 385.4 Hz (Soh-)
</pre>

=={{header|V (Vlang)}}==
{{trans|go}}
As an example, we analyze the .wav file (notes.wav) created by the [[https://rosettacode.org/wiki/Musical_scale#Vlang Musical Scale]] task.
<syntaxhighlight lang="v (vlang)">import os
import math
import encoding.binary

const (
    freqs = [261.6, 293.6, 329.6, 349.2, 392.0, 440.0, 493.9, 523.3]
    notes = ["Doh", "Ray", "Mee", "Fah", "Soh", "Lah", "Tee", "doh"]
)
 
fn get_note(freq f64) string {
    mut index := freqs.len
    for i in 0..freqs.len {
        if freq <= freqs[i] {
            index = i
            break
        }
    }
    match index {
0 {
   return "Doh-"
}
freqs.len {
   return "doh+"
}
else {
   if freqs[index]-freq <= freq-freqs[index-1] {
       return '${notes[index]}-'
   }
   return '${notes[index-1]}+'
}
    }
}
 
fn main() {
    mut file := os.open("notes.wav")?
    defer {
file.close()    
}
    mut hdr := []byte{len: 44}
    file.read(mut &hdr)?

    // check header parameters
    sample_rate := int(binary.little_endian_u32(hdr[24..28]))
    println("Sample Rate    : $sample_rate")
    data_length := int(binary.little_endian_u32(hdr[40..]))
    duration := data_length / sample_rate
    println("Duration       : $duration")
 
    mut sum := 0.0
    sample_rate_f := f64(sample_rate)
    mut data := []byte{len: sample_rate}
    nbytes := 20
    println("Bytes examined : $nbytes per sample")
    for _ in 0..duration {
        file.read(mut &data)?
        for i := 1; i <= nbytes; i++ {
            bf := f64(data[i]) / 32
            freq := math.asin(bf) * sample_rate_f / (f64(i) * math.pi * 2)
            sum += freq
        }
    }
    cav := sum / (f64(duration) * f64(nbytes))
    println("\nComputed average frequency = ${cav:.1} Hz (${get_note(cav)})")
 
    sum = 0.0
    for i in 0..freqs.len {
        sum += freqs[i]
    }
    aav := sum / f64(freqs.len)
    println("Actual average frequency   = ${aav:.1} Hz (${get_note(aav)})")
}</syntaxhighlight>

{{out}}
<pre>
Sample Rate    : 44100
Duration       : 8
Bytes examined : 20 per sample

Computed average frequency = 387.1 Hz (Soh-)
Actual average frequency   = 385.4 Hz (Soh-)</pre>

=={{header|Wren}}==
{{trans|Go}}
{{libheader|Wren-crypto}}
{{libheader|Wren-fmt}}
{{libheader|Wren-math}}
{{libheader|Wren-seq}}
We analyze the .wav file (musical_scale.wav) created by the [[Musical scale]] task.
<syntaxhighlight lang="wren">import "io" for File
import "./crypto" for Bytes
import "./fmt" for Fmt
import "./math" for Nums
import "./seq" for Lst

var freqs = [261.6, 293.6, 329.6, 349.2, 392.0, 440.0, 493.9, 523.3]
var notes = ["Doh", "Ray", "Mee", "Fah", "Soh", "Lah", "Tee", "doh"]

var getNote = Fn.new { |freq|
    var n = freqs.count
    var index = n
    for (i in 0...n) {
        if (freq <= freqs[i]) {
            index = i
            break
        }
    }
    if (index == 0) {
        return "Doh-"
    } else if (index == n) {
        return "doh+"
    } else {
        if (freqs[index] - freq <= freq - freqs[index-1]) {
            return notes[index] + "-"
        }
        return notes[index-1] + "+"
    }
}

var bytes = File.read("musical_scale.wav").bytes.toList
var hdr = bytes[0..43]

// check header parameters
var sampleRate = Bytes.toIntLE(hdr[24..27])
System.print("Sample Rate    : %(sampleRate)")
var dataLength = Bytes.toIntLE(hdr[40..-1])
var duration = dataLength / sampleRate
System.print("Duration       : %(duration)")

var sum = 0
var nbytes = 20
System.print("Bytes examined : %(nbytes) per sample") 
for (data in Lst.chunks(bytes[44..-1], sampleRate)) {
    for (i in 1..nbytes) {
        var bf = data[i] / 32
        var freq = bf.asin * sampleRate / (i * Num.pi * 2)
        sum = sum + freq
    }
}
var cav = sum / (duration * nbytes)
Fmt.print("\nComputed average frequency = $.1f Hz ($s)", cav, getNote.call(cav))
var aav = Nums.mean(freqs)
Fmt.print("Actual average frequency   = $.1f Hz ($s)", aav, getNote.call(aav))</syntaxhighlight>

{{out}}
<pre>
Sample Rate    : 44100
Duration       : 8
Bytes examined : 20 per sample

Computed average frequency = 387.1 Hz (Soh-)
Actual average frequency   = 385.4 Hz (Soh-)
</pre>

{{omit from|AWK}}
{{omit from|Blast}}
{{omit from|AutoHotkey}}
{{omit from|Befunge}}
{{omit from|GUISS}}
{{omit from|HTML}}
{{omit from|Lotus 123 Macro Scripting}}
{{omit from|Openscad}}
{{omit from|Scala}}
{{omit from|TPP}}
{{omit from|UNIX Shell}}

[[Category:Voice recognition]]
[[Category:Waveform analysis]]