[How To] Find Similar Sounding Names | Cologne Phonetics asp.net c#

Scope

So we will first discuss about the scope of finding similar sound strings or words first. Mainly these methods are used for data analysis. Some of examples are criminal lists matching, finding black listed peoples etc.

Here I'm giving you implementation of Cologne Phonetics algorithm. This phonetics algorithm will represent a word as sequence of digits. So, for example it will return same digits code for names like "Mary", "Marie", which sounds same right?

you can check what codes will generate for different names by using this online implementation. Go to the link and enter the name in text box. Click on the Encode button, will show you the generated code for the name you have entered.

Cologne Phonetics asp.net c#

Implementation of Cologne phonetics algorithm is given below. It is just a simple class.

    /// <summary>
    /// Transforms a word into the respective Cologne Phontetics notation
    /// </summary>
    public class ColognePhonetics
    {

        /// <summary>
        /// Group of letters with value "0"
        /// </summary>
        private static char[] group0 = new char[] { 'A', 'E', 'I', 'J', 'O', 'U', 'Y', 'Ä', 'Ö', 'Ü' };

        /// <summary>
        /// Group of letters with value "3"
        /// </summary>
        private static char[] group3 = new char[] { 'F', 'V', 'W' };

        /// <summary>
        /// Group of letters with value "4"
        /// </summary>
        private static char[] group4 = new char[] { 'G', 'K', 'Q', };

        /// <summary>
        /// Group of letters with value "6"
        /// </summary>
        private static char[] group6 = new char[] { 'M', 'N' };

        /// <summary>
        /// Group of letters with value "8"
        /// </summary>
        private static char[] group8 = new char[] { 'S', 'Z', 'ß' };

        /// <summary>
        /// Group of letters following an initial "C"
        /// </summary>
        private static char[] groupCFirst = new char[] { 'A', 'H', 'K', 'L', 'O', 'Q', 'R', 'U', 'X' };

        /// <summary>
        /// Group of letters following a "C" within the string
        /// </summary>
        private static char[] groupCNoFirst = new char[] { 'A', 'H', 'K', 'O', 'Q', 'U', 'X' };

        /// <summary>
        /// Group of letters that can precede a "C"
        /// </summary>
        private static char[] groupCPrevious = new char[] { 'S', 'Z' };

        /// <summary>
        /// Group of letters that can precede a "D" or "T"
        /// </summary>
        private static char[] groupDTPrevious = new char[] { 'C', 'S', 'Z' };

        /// <summary>
        /// Group of letters following an "X"
        /// </summary>
        private static char[] groupXFollow = new char[] { 'C', 'K', 'Q' };

        /// <summary>
        /// Process all three steps of encoding the Cologene Phonetics
        /// </summary>
        /// <param name="input"></param>
        /// <returns></returns>
        public static string GetPhonetics(string input)
        {
            try
            {
                var output = GetEncoding(input);
                output = CleanDoubles(output);
                output = CleanZeros(output);
                return output;
            }
            catch (Exception ex)
            {
                return null;
            }
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="input"></param>
        /// <returns></returns>
        public static string GetEncoding(string input)
        {
            char[] content = input.ToUpperInvariant().ToCharArray();

            // hold result in StringBuilder
            StringBuilder sb = new StringBuilder();

            for (int i = 0; i < content.Length; i++)
            {
                char entry = content[i];

                // ignore non-letters
                if (!Char.IsLetter(entry))
                {
                    continue;
                }

                // ignore H
                if (entry.Equals('H'))
                {
                    continue;
                }

                // check if entry is part of the standard value groups

                if (group0.Contains(entry))
                {
                    sb.Append("0");
                    continue;
                }

                if (group3.Contains(entry))
                {
                    sb.Append("3");
                    continue;
                }

                if (group4.Contains(entry))
                {
                    sb.Append("4");
                    continue;
                }

                if (group6.Contains(entry))
                {
                    sb.Append("6");
                    continue;
                }

                if (group8.Contains(entry))
                {
                    sb.Append("8");
                    continue;
                }

                if (entry.Equals('B'))
                {
                    sb.Append("1");
                    continue;
                }

                if (entry.Equals('L'))
                {
                    sb.Append("5");
                    continue;
                }

                if (entry.Equals('R'))
                {
                    sb.Append("7");
                    continue;
                }

                // check if character is in a special value group

                if (entry.Equals('P'))
                {
                    // last letter in array?
                    if (i + 1 >= content.Length)
                    {
                        sb.Append("1");
                        continue;
                    }

                    char next = content[i + 1];

                    // if followed by "H"
                    if (next.Equals('H'))
                    {
                        sb.Append("3");
                        continue;
                    }

                    sb.Append("1");
                    continue;
                }

                if (entry.Equals('X'))
                {
                    // if first letter
                    if (i == 0)
                    {
                        sb.Append("48");
                        continue;
                    }

                    char previous = content[i - 1];

                    // compare with previous
                    if (groupXFollow.Contains(previous))
                    {
                        sb.Append("8");
                        continue;
                    }

                    sb.Append("48");
                    continue;
                }

                if (entry.Equals('D') || entry.Equals('T'))
                {
                    // last letter in array?
                    if (i + 1 >= content.Length)
                    {
                        sb.Append("2");
                        continue;
                    }

                    char next = content[i + 1];

                    // is next value in special value group?
                    if (groupDTPrevious.Contains(next))
                    {
                        sb.Append("8");
                        continue;
                    }

                    sb.Append("2");
                    continue;
                }

                if (entry.Equals('C'))
                {
                    // if first letter
                    if (i == 0)
                    {
                        char next = content[i + 1];

                        // if next letter is in same group
                        if (groupCFirst.Contains(next))
                        {
                            sb.Append("4");
                            continue;
                        }

                        sb.Append("8");
                        continue;
                    }
                    else // not first letter
                    {
                        // last letter?
                        if (i + 1 >= content.Length)
                        {
                            continue;
                        }

                        char next = content[i + 1];
                        char previous = content[i - 1];

                        // is previous letter in same group?
                        if (groupCPrevious.Contains(previous))
                        {
                            sb.Append("8");
                            continue;
                        }
                        else
                        {
                            // is next letter in same group?
                            if (groupCNoFirst.Contains(next))
                            {
                                sb.Append("4");
                                continue;
                            }

                            sb.Append("8");
                            continue;
                        }
                    }
                }
            }

            return sb.ToString();
        }

        /// <summary>
        /// Remove duplicate, adjacent values 
        /// </summary>
        /// <param name="input"></param>
        /// <returns></returns>
        public static string CleanDoubles(string input)
        {
            StringBuilder sb = new StringBuilder();
            char[] content = input.ToCharArray();
            char previous = new char();

            for (int i = 0; i < content.Length; i++)
            {
                char entry = content[i];
                if (!entry.Equals(previous))
                {
                    sb.Append(entry);
                }
                previous = entry;
            }
            return sb.ToString();
        }

        /// <summary>
        /// Remove zeros, except at the beginning
        /// </summary>
        /// <param name="input"></param>
        /// <returns></returns>
        public static string CleanZeros(string input)
        {
            StringBuilder sb = new StringBuilder();
            char[] content = input.ToCharArray();

            for (int i = 0; i < content.Length; i++)
            {
                char entry = content[i];

                // skip all zeros except in first place
                if (!entry.Equals('0') || i == 0)
                {
                    sb.Append(entry);
                }
            }
            return sb.ToString();
        }
    }

To get the code call GetPhonetics method in the above class. Implementation is given below

string soundCode=ColognePhonetics.GetPhonetics("John");

string soundCode holds code for the name John.