In this blog post, we will look at the reasons why the voice on a phone call sounds different from the actual voice and the technical principles behind it.
One of the most impressive aspects of dealing with criminals in movies is the voice of the criminal. When the screen goes dark and the character on the screen answers the phone, the criminal’s strange voice instantly raises the tension to the highest level. In a similar way, the voice of the phone in various movies plays an important role in instilling fear in the audience. In particular, the scene in which the voice of the kidnapper is heard over the phone line is threatening just by the voice alone. Many people may think that the voice heard in the movie is a simple production technique, but the reason why the voice on the phone sounds different from the original voice is due to actual technical causes.
In reality, there is a difference between the voice heard on a phone call and the voice of a person when they are actually talking. This is due to the modulation that occurs during the process of converting voice into electrical signals and transmitting them. The original voice undergoes various changes in sound quality, tone, and frequency range simply by going through a mechanical process. Therefore, law enforcement agencies have limitations in identifying criminals based on voice over the phone alone. In particular, some movies intentionally distort the voice over the phone to create a frightening atmosphere.
Let’s take a look at how a phone works and how voice modulation is achieved. The basic principle of a phone is to convert voice into an electrical signal and then transmit it to the other party. In this process, the voice signal is divided into two major steps. The first step is the process of the microphone converting sound into an electrical signal. The second step is the process of transmitting that signal so that the receiver can reproduce it as sound through the speaker. At this time, the voice frequencies transmitted by telephone signals are limited to about 300 Hz to 3,400 Hz. The entire human voice frequency band ranges from about 20 Hz to 20,000 Hz, and the frequencies transmitted by the telephone only cover a portion of this range. As a result, much of the low and high-pitched parts of human voice are lost.
This frequency band limitation is an important cause of the criminal’s voice sounding different. In movies and real-life phone calls, the voice sounds flatter and less resonant due to this limited frequency band, and the high pitch is emphasized. In reality, the voice on the phone sounds sharper and more unfamiliar than it originally did. Therefore, this is sometimes used in crime movies to make the criminal’s voice sound even more bizarre.
In addition, when voice-modulation technology is used in crime movies, it is often used to add specific sound effects to heighten the sense of fear. In particular, in scenes where a kidnapping or blackmail call is received, these sound effects act as a dramatic element. Generally, the high and low frequencies are emphasized at the same time or an irregular electronic sound effect is added to make the viewer feel the psychological tension of the person receiving the call more realistically. Adding a tremor or echo to a voice is another technique often used to create a frightening atmosphere.
This kind of voice modulation does not only serve as a cinematic technique, but also plays an important role in actual criminal investigations. Investigative agencies try to identify the identity of a criminal through voice modulation and voice analysis in cases involving phone threats or unidentified persons. This includes techniques that analyze specific frequencies to identify unique characteristics of a voice or match a voice to a specific person by examining the timbre. Recently, with the development of voice analysis technology using artificial intelligence (AI), it has become possible to analyze even the subtle characteristics of a voice that were previously indistinguishable.
As such, the modulation of voice and sound effects in telephone calls are not just simple devices, but have real-world implications. In particular, they are used dramatically in movies to create a sense of tension in the audience by making them feel nervous just by hearing the voice of a criminal. In real life, we feel psychological pressure just by hearing a voice, which shows how important voice differences are in telephone-based criminal investigations.
