Presently, there is a wider range of tools used in the production of audio media as compared to the past. Better methods of manipulating and capturing audio are developed with each passing day, to enhance the quality of recorded sound.
Apart from PDAs and laptops, the assortment of the available equipment used for audio recording include: tape recorders, memory recorders, disk recorders, and analogue and digital recording equipment. The main aim of this article is to assist you to make an informed decision when getting ready to buy audio recording equipment.
The information contained on this page is meant for a diverse group of people including students, speech therapists and researchers. The article largely focuses on handy equipment that can be used to capture audio media in the field within the available budget (the most expensive recorder mentioned goes for £650), which therefore excludes complex recording equipment used by Radio broadcasters or for mass communication in general.
The objective is to help you assemble an assortment of tools and equipment that have the capability to produce excellent audio recordings, which are good enough to be used for signal analysis. An example would be the use of a computer in the analysis of the vocal sound quality, format frequencies and fundamental frequencies. The audio recorders currently available in the market are meticulously constructed to ensure that all vocal recordings to be used in the instrumental analysis process are of good quality. This quality of vocal output is attained by ensuring that you have the right choice of a recorder, the perfect microphone and a good recording environment that is free from noise – ensuring that the audio recording settings are set to precision.
For each of the mention recorders their basic functions, advantages and short comings are mentioned. However, technology is constantly improving at a rapid pace. This means that what is relevant today might be outdated within the shortest period of time.
The Use of Cassette Recorders in the Audio Recording Process
Cassette recorders are amongst some of the sound recording devices which have been around for a while. Initially the recorders utilized 1/8″ tapes with 1.875 inches/sec recording speeds. Modern cassette recorders were tweaked for efficient speech recordings, but they are generally unforgiving when the recording levels are not set correctly. They are not the best devices to be used when high-quality speech recordings are required. This is because they are prone to harmonic distortion and degenerating quality after years of storage. In the 90’s walkman recorders were the most preferred cassette-based audio recorders. Today it is difficult to find a walkman recorder in the market, because they have been edged out of the market digital audio recorders. However, before digital recorders came along the Minidisc Recorders were preferred largely because of their compact nature and disk use.
Using Minidisc Recorders for Speech Audio Recording
This kind of audio recorder produces compressed audio media on a 2.5 inch magneto-photosensitive disk. A cartridge is used to shield the disks from damage. The ATRAC compression system invented by Sony is used to produce the audio media. These recorders are amazingly small in size and highly portable, with a great capacity of audio data handling. On the flip side, their small size makes them difficult to handle and operate.
The Minidisc recorders are designed to deter people using them from copywriting audio media, meaning you are not able to directly get rights to the compressed sequence bits that make up audio media. You have to compress and recompress the media before it can be used, and the compression and recompression process leads to loss of playback sound quality. A number of minidisc recorders are equipped with digital output capabilities to facilitate the transfer of audio media to a computer, but in order to do this you will require a PC with a digital audio input and a minidisc deck that has a digital output.
Currently there is a deliberation to decide whether there is any variance in speech recordings when using ATRAC compression method and whether it would affect instrumental analysis. Considering that the method is basically a time-domain coding that is used on varying frequency signals, the pitch is not likely to be affected by coding. However, the spectral envelope might be affected and there is no guarantee that it would not be negatively modified. It is difficult to know what effect compression will have on a recording, however small or negligible the change may have been the uncertainty is what causes a lot of concern.
The HiMD recorder is the latest recorder to be produced in the Minidisc recorder category. This new minidisc has two fascinating aspects that set it apart from the older models. For one, the HiMD recorders come with a Universal Serial Bus (USB) interface which has the capability to load audio media into a computer, which is only possible if they were produced on a recorder that supports analogue input.
Secondly, they utilize disks with higher memory capacities enabling the recording of vocal media for an hour or longer; whether in a compressed or uncompressed mode. One of the HiMD Minidisc recorders available in the market at the moment is the Sony NH700. It captures audio media in ATRAC3plus and Linear PCM recording to Hi-MD up to 1 GB. Normal MD blanks are reformatted to 300MB functionality since you can now use it as a USB disk. Doing so facilitates the use of a PC to transfer audio media from the line input.
The use of (DAT) Digital Audio Tape Recorders to Capture Audio Speech
Digital Audio Tape recorders were designed to capture digital audio recordings on 6mm tapes. The recorders used an enhanced video recording technique, with rotating tape heads. DAT recorders have the ability to capture high-quality audio recordings, and they gained wide use in the broadcasting professional. The recorders capture PCM digital signals in 16-bit linear recordings at either 48000 or 44100 samples/sec speeds. Most AT recorders come with a digital output mechanism, enabling the digital transfer of recordings to computer systems. One of the main concerns about DAT recorders is their tape transport system and rotating head complexity. The devices are highly sensitive and they require regular maintenance and a high level of protection during transit.
Using the Solid-state Digital Voice Recorders to Record Speech
The solid-state recorders store audio recordings on memory cards loaded on the device. The recorders often come with the choice to save the recorded audio either in compressed forms line the MP3 format or as uncompressed linear PCM formats. With larger memory card capacities, the solid-state recorders can record longer sessions on the compressed formats; however, in such instances the quality of the recorded audio is often lower in quality. Audio recordings intended for computer analysis should be recorded at data rates of about 192kbps to obtain quality recordings. In the uncompressed monophonic format, a one hour 16-bit recording recorded at a 44100samples/sec speed occupies a space of about 320MB. However, if the recording is maintained at a 192kbps data rate, the recording occupies only about 90MB of space.
Recording Speech Using Hard-Disk Recorders
Hard-disk recorders store both uncompressed and compressed audio recordings onto in-built disk drives with high storage capacities. The recordings are transferable to computers or they can be copied to CDs. There are few hard drive recorders in the market at the moment, but their use promises to increase progressively as a number of people embrace the new technology. One of the main reasons why they are not in high circulation is because they tend to be very expensive and they are generally not designed with portability in mind. However, a number of compact music players are available in the market and most come with live recording functionalities. They store the recorded audio on in-built low capacity in-built hard-disks, and come with external sockets to accommodate microphones. The iRiver H300 is an example of these portable music players, and it comes with about 20 to 40GB hard disk storage spaces. The recordings are then transferable to computer systems via USB ports.
Recording Audio Using Laptop Interfaces
Laptops can be transformed into digital recorders, if equipped with high-quality external microphones. However, most laptops have sub-par microphone inputs and they are usually too insensitive to act as proper quality microphones. A separate digital converter and microphone pre-amplifier are required to work in collaboration with laptops for quality audio recording. With the introduction of USB microphone interfaces such as the M-Audio MobilePre have made the process much simpler. The USB interface comes with 3.5 mm microphone ports and it can support XLR cable connections. It can also supply Condenser microphones with phantom power and it is relatively efficient when it comes to noise reduction. It is important to have quality recording software installed on the laptop, with the ability to create audio files and store them on the computer system.
Using PDAs as Audio Recorders
PDAs or Palm-top computers have the ability to be used as portable audio recorders. These devices are often preferred for audio recording when compared to conventional computer systems, because they are highly portable, less expensive and come with better battery life. PDAs and Palm-tops also come equipped with network and memory interfaces making them the ideal option when compared to conventional computers. Few PDAs come with microphones and those that do are designed specifically for voice recording as opposed to quality audio recordings. PDAs are usually designed for telephony purposes with combination of a headset and microphone. For the purposes of quality audio recording, a Compact Flash interface accompanied with a quality pre-amplifier will be required to facilitate external microphone use.
Choosing a Microphone to Accompany the Selected Audio Recorder
Once an appropriate audio recorder has been selected, the next step is to choose a compatible microphone to accompany the recorder. The chosen microphone should be compatible to the recorder when it comes to connection and quality. Using a sub-par microphone with a quality recorder will result in equally sub-par audio recordings and vice versa.
The different types of microphones available
There are essentially two main types of microphones available in the market; the Condenser microphones and Dynamic microphones.
Dynamic microphones are considered as the ‘general-purpose’ microphones. They accommodate rough handling, because they are quite sturdy and flexible. They are the ideal choice for audio recordings where high volume levels cannot be avoided for example when amplifiers and musical instruments are part of the audio recording. They do not have internal amplifiers and external power sources or batteries.
Condenser microphones are more sensitive and they require external power sources or batteries. They are known to produce stronger audio signals and they are generally more responsive compared to dynamic microphones. They are however not ideal for audio recordings in high volume situations, because of their high sensitivity.
The different types of microphone connectors
Microphones come with different types of connectors, and this is an important aspect which should not be overlooked because it determines the microphone’s comparability with the audio recorder when it comes to connectivity. Although conversion cables are available to enable a microphone to be used with an incompatible recorder, it is much simpler to get a microphone which is connector-compatible with the recorder at hand.
The XLR connectors commonly accompany professional microphones. Each microphone comes with earthed shields and two signal lines. They are known to provide the best amount resistance to electrical-based interferences.
The Mini XLR connectors accompany lapel or lavalier microphones. The connector essentially connects the microphone to a radio transmitter or battery box. The other end of the battery box often has 1/4″ jack connectors or XLR connectors.
1/4″(6.5mm) stereo or mono jack connectors commonly accompany stereo microphones and professional microphones respectively.
1/8″ (3.5mm) stereo or mono jacks commonly accompany consumer-based stereo and mono microphones.
3.5mm mini jacks commonly accompany telephony headsets, which come with mono microphones and stereo headphones.
